00008813092012-10-012012-10-010000881309fmst:S000006860Member2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000018537Member2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000018538Member2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000018539Member2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000040036Member2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000018537Memberrr:AfterTaxesOnDistributionsMember2012-10-012012-10-010000881309fmst:S000006860Memberfmst:C000018537Memberrr:AfterTaxesOnDistributionsAndSalesMember2012-10-012012-10-010000881309fmst:S000006860Memberfmst:Index8Member2012-10-012012-10-010000881309fmst:S000006861Member2012-10-012012-10-010000881309fmst:S000006861Memberfmst:C000018540Member2012-10-012012-10-010000881309fmst:S000006861Memberfmst:C000018540Memberrr:AfterTaxesOnDistributionsMember2012-10-012012-10-010000881309fmst:S000006861Memberfmst:C000018540Memberrr:AfterTaxesOnDistributionsAndSalesMember2012-10-012012-10-010000881309fmst:S000006861Memberfmst:Index8Member2012-10-012012-10-01 iso4217:USD xbrli:pure xbrli:shares iso4217:USD xbrli:shares 0000881309FRANKLIN MUNICIPAL SECURITIES TRUST485BPOS2012-09-272012-10-012012-05-31false2012-10-01~ http://xbrl.sec.gov/rr/role/RiskReturnDetail column period compact * row primary compact * ~Fund SummaryInvestment GoalTo provide investors with a high level of income exempt from federal and California personal income taxes. Its secondary goal is capital appreciation to the extent possible and consistent with its principal investment goal.Fees and Expenses of the FundYou may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds.100000These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 43 in the Fund's Prospectus and under “Buying and Selling Shares” on page 38 of the Fund’s Statement of Additional Information.SHAREHOLDER FEES (fees paid directly from your investment)~ http://xbrl.sec.gov/rr/role/ShareholderFeesData column dei_LegalEntityAxis compact fmst_S000006860Member column rr_ProspectusShareClassAxis compact * row primary compact * ~0.04250.000.000.000.000.04000.01000.00<div><p>ANNUAL FUND OPERATING EXPENSES</p><p>(expenses that you pay each year as a percentage of the value of your investment)</p></div>~ http://xbrl.sec.gov/rr/role/OperatingExpensesData column dei_LegalEntityAxis compact fmst_S000006860Member column rr_ProspectusShareClassAxis compact * row primary compact * ~0.00470.00470.00470.00470.00100.00640.00650.000.00050.00050.00050.00050.00620.01160.01170.0052ExampleThis Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:4866157561166~ http://xbrl.sec.gov/rr/role/ExpenseExample column dei_LegalEntityAxis compact fmst_S000006860Member column rr_ProspectusShareClassAxis compact * row primary compact * ~5186688381258219372644142053167291653If you do not sell your shares:~ http://xbrl.sec.gov/rr/role/ExpenseExampleNoRedemption column dei_LegalEntityAxis compact fmst_S000006860Member column rr_ProspectusShareClassAxis compact * row primary compact * ~11836863812581193726441420Portfolio Turnover0.0667<div><p>The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 6.67% of the average value of its portfolio.</p></div>Principal Investment StrategiesUnder normal market conditions, the Fund invests at least 80% of its net assets in municipal securities whose interest is free from regular federal income taxes and from California personal income taxes.<div><p>Under normal market conditions, the Fund invests at least 80% of its net assets in municipal securities whose interest is free from regular federal income taxes and from California personal income taxes. Although the Fund tries to invest all of its assets in securities whose interest is free from regular federal and California personal income taxes, it is possible, although not anticipated, that up to 20% of its net assets may be in securities that pay taxable interest. The Fund also may have up to 100% of its assets in securities that pay interest subject to the federal alternative minimum tax.</p><p>The Fund may invest in municipal securities rated in any rating category by U.S. nationally recognized rating services, including securities rated below investment grade (or comparable unrated or short-term rated securities).</p><p>The Fund also may invest up to 35% of its total assets in municipal securities issued by U.S. territories.</p><p>Although the investment manager will search for investments across a large number of municipal securities that finance different types of projects, from time to time, based on economic conditions, the Fund may have significant positions in municipal securities that finance similar types of projects.</p><p>The investment manager selects securities that it believes will provide the best balance between risk and return within the Fund&#146;s range of allowable investments and typically uses a buy and hold strategy. This means it generally holds securities in the Fund&#146;s portfolio for income purposes, rather than trading securities for capital gains, although the investment manager may sell a security at any time if it believes it could help the Fund meet its goal.</p><p>The investment manager may consider existing market conditions, the availability of lower-rated securities, and whether the difference in yields between higher- and lower-rated securities justifies the higher risk of lower-rated securities when selecting securities for the Fund&#146;s portfolio. Thus, there may be times when the Fund has a majority of its investments in securities that are considered investment grade.</p></div>Principal Risks<div><p>You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.</p><p>Interest Rate</p><p>When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. In general, securities with longer maturities are more sensitive to these interest rate changes.</p><p>Market</p><p>The market values of securities owned by the Fund will go up or down, sometimes rapidly or unpredictably. A security&#146;s market value may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all securities. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.</p><p>Credit</p><p>An issuer of debt securities may fail to make interest payments and repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.</p><p>A change in the credit rating of a municipal bond insurer that insures securities in the Fund&#146;s portfolio may affect the value of the securities it insures, the Fund&#146;s share price and Fund performance. The Fund might also be adversely impacted by the inability of an insurer to meet its insurance obligations.</p><p>High-Yield Debt Securities</p><p>Issuers of lower-rated or "high-yield" debt securities are not as strong financially as those issuing higher credit quality debt securities. These issuers are more likely to encounter financial difficulties and are more vulnerable to changes in the relevant economy, such as a recession or a sustained period of rising interest rates, that could affect their ability to make interest and principal payments when due. The prices of high-yield debt securities generally fluctuate more than those of higher credit quality. High-yield debt securities are generally more illiquid (harder to sell) and harder to value.</p><p>California and U.S. Territories</p><p>Because the Fund invests predominantly in California municipal securities, events in California are likely to affect the Fund's investments and its performance. These events may include economic or political policy changes, tax base erosion, state constitutional limits on tax increases, budget deficits and other financial difficulties, and changes in the credit ratings assigned to municipal issuers of California. As with California municipal securities, events in any of the territories where the Fund is invested may affect the Fund's investments and its performance.</p><p>Focus</p><p>The Fund may invest more than 25% of its assets in municipal securities that finance similar types of projects, such as utilities, hospitals, higher education, transportation and real estate. A change that affects one project, such as proposed legislation on the financing of the project, a shortage of the materials needed for the project, or a declining need for the project, would likely affect all similar projects, thereby increasing market risk.</p><p>Tax-Exempt Securities</p><p>While the Fund endeavors to purchase only bona fide tax-exempt securities, there are risks that: (a) a security issued as tax-exempt may be reclassified as taxable by the Internal Revenue Service or a state tax authority, and/or (b) future legislative, administrative or court actions could adversely impact the qualification of income from a tax-exempt security as tax-free. Such reclassifications or actions could cause interest from a security to become taxable, possibly retroactively, subjecting you to increased tax liability.</p><p>Income</p><p>Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall or when the Fund experiences defaults on debt securities it holds.</p><p>Prepayment</p><p>Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest.</p><p>Unrated Debt Securities</p><p>Unrated debt securities determined by the investment manager to be of comparable quality to rated securities which the Fund may purchase may pay a higher interest rate than such rated debt securities and be subject to a greater risk of illiquidity or price changes. Less public information is typically available about unrated securities or issuers.</p><p>Management</p><p>The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.</p></div>PerformanceThe following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance.The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.(800) DIAL BEN/342-5236franklintempleton.comSales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.<div><p>The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.</p><p>Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.</p></div>CLASS A ANNUAL TOTAL RETURNS0.06770.05790.07000.06730.0630-0.0164-0.19970.28240.04940.1455~ http://xbrl.sec.gov/rr/role/BarChartData column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_LegalEntityAxis compact fmst_S000006860Member ~Best Quarter:2009-09-300.1492Worst Quarter:2008-12-31-0.1429As of June 30, 2012, the Fund's year-to-date return was 8.37%.<table style="font: 11px sans-serif; background-color:#DDDDDD" border="0" cellspacing="0" cellpadding="5" width="745"><tr><td style="border-bottom: 2px solid #ffffff;" valign="top">Best Quarter:</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">Q3'09</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">14.92%</td></tr><tr><td style="border-bottom: 2px solid #ffffff;" valign="top">Worst Quarter:</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">Q4'08</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">-14.29%</td></tr><tr><td style="border-bottom: 2px solid #ffffff;" valign="top" colspan="3">As of June 30, 2012, the Fund's year-to-date return was 8.37%.</td></tr></table><div><p>AVERAGE ANNUAL TOTAL RETURNS<br/>(figures reflect sales charges)</p><p>For the periods ended December 31, 2011</p></div>~ http://xbrl.sec.gov/rr/role/PerformanceTableData column dei_LegalEntityAxis compact fmst_S000006860Member column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~Return Before Taxes0.09680.03040.04770.09680.03040.04770.08230.03300.04820.09880.03040.04760.12860.03380.04650.14650.04080.05280.10700.05220.0538<div><p>Historical performance for Advisor Class shares prior to their inception is based on the performance of Class A shares. Advisor Class performance has been adjusted to reflect differences in sales charges between classes.</p><p>The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are shown only for Class A and after-tax returns for other classes will vary.</p></div>Investment GoalTo maximize income exempt from federal income taxes and from the personal income taxes for resident shareholders of Tennessee to the extent consistent with prudent investing and the preservation of shareholders' capital.Fees and Expenses of the FundYou may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds.100000These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 43 in the Fund's Prospectus and under “Buying and Selling Shares” on page 38 of the Fund’s Statement of Additional Information.SHAREHOLDER FEES (fees paid directly from your investment)~ http://xbrl.sec.gov/rr/role/ShareholderFeesData column dei_LegalEntityAxis compact fmst_S000006861Member column rr_ProspectusShareClassAxis compact * row primary compact * ~0.04250.00<div><p>ANNUAL FUND OPERATING EXPENSES</p><p>(expenses that you pay each year as a percentage of the value of your investment)</p></div>~ http://xbrl.sec.gov/rr/role/OperatingExpensesData column dei_LegalEntityAxis compact fmst_S000006861Member column rr_ProspectusShareClassAxis compact * row primary compact * ~0.00540.00100.00070.0071-0.00010.0070ExampleThis Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects adjustments made to the Fund's operating expenses due to the fee waiver and/or expense reimbursement by the investment manager and/or administrator for the 1 Year numbers only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:4936418021269~ http://xbrl.sec.gov/rr/role/ExpenseExample column dei_LegalEntityAxis compact fmst_S000006861Member column rr_ProspectusShareClassAxis compact * row primary compact * ~Portfolio Turnover0.0571<div><p>The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 5.71% of the average value of its portfolio.</p></div>Principal Investment StrategiesUnder normal market conditions, the Fund invests at least 80% of its net assets in investment grade municipal securities whose interest is free from regular federal income taxes and from Tennessee personal income taxes.<div><p>Under normal market conditions, the Fund invests at least 80% of its net assets in investment grade municipal securities whose interest is free from regular federal income taxes and from Tennessee personal income taxes. Although the Fund tries to invest all of its assets in securities whose interest is free from regular federal and Tennessee personal income taxes, it is possible, although not anticipated, that up to 20% of its net assets may be invested in securities that pay taxable interest. The Fund also may have up to 100% of its assets in securities that pay interest subject to the federal alternative minimum tax.</p><p>The Fund only buys municipal securities rated, at the time of purchase, in one of the top four ratings categories by one or more U.S. nationally recognized rating services (or comparable unrated or short-term rated securities).</p><p>The Fund may invest up to 35% of its assets in municipal securities issued by U.S. territories.</p><p>Although the investment manager will search for investments across a large number of municipal securities that finance different types of projects, from time to time, based on economic conditions, the Fund may have significant positions in municipal securities that finance similar types of projects.</p><p>The investment manager selects securities that it believes will provide the best balance between risk and return within the Fund&#146;s range of allowable investments and typically uses a buy and hold strategy. This means it generally holds securities in the Fund&#146;s portfolio for income purposes, rather than trading securities for capital gains, although the investment manager may sell a security at any time if it believes it could help the Fund meet its goal.</p></div>Principal Risks<div><p>You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.</p><p>Interest Rate</p><p>When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. In general, securities with longer maturities are more sensitive to these interest rate changes.</p><p>Market</p><p>The market values of securities owned by the Fund will go up or down, sometimes rapidly or unpredictably. A security&#146;s market value may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all securities. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.</p><p>Credit</p><p>An issuer of debt securities may fail to make interest payments and repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.</p><p>A change in the credit rating of a municipal bond insurer that insures securities in the Fund&#146;s portfolio may affect the value of the securities it insures, the Fund&#146;s share price and Fund performance. The Fund might also be adversely impacted by the inability of an insurer to meet its insurance obligations.</p><p>Tennessee and U.S. Territories</p><p>Because the Fund invests predominantly in Tennessee municipal securities, events in Tennessee are likely to affect the Fund's investments and its performance. These events may include economic or political policy changes, tax base erosion, state constitutional limits on tax increases, budget deficits and other financial difficulties, and changes in the credit ratings assigned to municipal issuers of Tennessee. As with Tennessee municipal securities, events in any of the territories where the Fund is invested may affect the Fund's investments and its performance.</p><p>Focus</p><p>The Fund may invest more than 25% of its assets in municipal securities that finance similar types of projects, such as utilities, hospitals, higher education, transportation and real estate. A change that affects one project, such as proposed legislation on the financing of the project, a shortage of the materials needed for the project, or a declining need for the project, would likely affect all similar projects, thereby increasing market risk.</p><p>Tax-Exempt Securities</p><p>While the Fund endeavors to purchase only bona fide tax-exempt securities, there are risks that: (a) a security issued as tax-exempt may be reclassified as taxable by the Internal Revenue Service or a state tax authority, and/or (b) future legislative, administrative or court actions could adversely impact the qualification of income from a tax-exempt security as tax-free. Such reclassifications or actions could cause interest from a security to become taxable, possibly retroactively, subjecting you to increased tax liability.</p><p>Income</p><p>Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall or when the Fund experiences defaults on debt securities it holds.</p><p>Prepayment</p><p>Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest.</p><p>Management</p><p>The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.</p></div>PerformanceSales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.<div><p>The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for shares of the Fund. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.</p><p>Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.</p></div>ANNUAL TOTAL RETURNS0.09210.05500.04900.03280.04250.0265-0.03590.13490.00680.1133~ http://xbrl.sec.gov/rr/role/BarChartData column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_LegalEntityAxis compact fmst_S000006861Member ~Best Quarter:2009-09-300.0593Worst Quarter:2010-12-31-0.0537As of June 30, 2012, the Fund's year-to-date return was 4.21%.<table style="font: 11px sans-serif; background-color:#DDDDDD" border="0" cellspacing="0" cellpadding="5" width="745"><tr><td style="border-bottom: 2px solid #ffffff;" valign="top">Best Quarter:</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">Q3'09</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">5.93%</td></tr><tr><td style="border-bottom: 2px solid #ffffff;" valign="top">Worst Quarter:</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">Q4'10</td><td style="border-bottom: 2px solid #ffffff;" valign="bottom" align="right">-5.37%</td></tr><tr><td style="border-bottom: 2px solid #ffffff;" valign="top" colspan="3">As of June 30, 2012, the Fund's year-to-date return was 4.21%.</td></tr></table><div><p>AVERAGE ANNUAL TOTAL RETURNS<br/>(figures reflect sales charges)</p><p>For the periods ended December 31, 2011</p></div>~ http://xbrl.sec.gov/rr/role/PerformanceTableData column dei_LegalEntityAxis compact fmst_S000006861Member column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~Return Before Taxes0.06620.03810.04600.06620.03810.04600.05710.03820.04540.10700.05220.0538<div><p>The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown.</p></div>New or additional investments into Class B are no longer permitted. The investment manager and administrator have contractually agreed to waive or assume certain expenses so that common expenses (excluding Rule 12b-1 fees) do not exceed 0.60% (other than certain non-routine expenses) until September 30, 2013. Contractual fee waiver and/or expense reimbursement agreements may not be terminated during the terms set forth above.