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Prospectus Date

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Feb. 29, 2012

Tax-Exempt Bond Fund formerly Tax-Exempt Bond Fund I (Prospectus Summary): | Tax-Exempt Bond Fund formerly Tax-Exempt Bond Fund I

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TAX-EXEMPT BOND FUND    

Supplement Text

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Supplement dated June 15, 2012

to the Class A, Class B, Class C, and Class P Shares Prospectus

for Principal Funds, Inc.

dated February 29, 2012

(as supplemented on March 16, 2012, March 29, 2012, April 9, 2012, April 20, 2012, and May 11, 2012)

This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus.

FUND SUMMARIES

Investment Strategy, Heading

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Under the Principal Investment Strategies heading, delete the last sentence in the paragraph and substitute:    

Investment Strategy, Narrative

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Under normal circumstances, the Fund maintains an average portfolio duration that is within ±50% of the  

duration of the Barclays Capital Municipal Bond Index, which as of December 31, 2011 was 8.08 years.  

Tax-Exempt Bond Fund formerly Tax-Exempt Bond Fund I | Class A

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PTEAX

Tax-Exempt Bond Fund formerly Tax-Exempt Bond Fund I | Class B

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Trading Symbol

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PTBBX

Tax-Exempt Bond Fund formerly Tax-Exempt Bond Fund I | Class C

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Trading Symbol

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PTBCX