X0306 4 2013-03-04 0001022079 QUEST DIAGNOSTICS INC DGX 0001222679 PREVOZNIK MICHAEL E C/O QUEST DIAGNOSTICS INCORPORATED 3 GIRALDA FARMS MADISON NJ 07940 1 SVP & General Counsel Common Stock 2013-03-04 4 F 0 463 55.97 D 45898 D Common Stock 2013-03-06 4 S 0 778 56.6364 D 45128 D Common Stock 4429 I 401k/SDCP Disposition of common stock to the issuer solely to cover tax withholding obligations arising from the vesting of a previous grant of restricted share units. The sale reported was effected pursuant to a Rule 10b5-1 sales plan adopted by the reporting person on February 7, 2011. This transaction was executed in multiple trades at prices ranging from $56.58 to $56.6616. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. The amount includes exempt purchases made under the Company's stock purchase plan since the date of the last filing on Form 4. These underlying shares were acquired on a periodic basis by the trustee of the Company's tax qualified Profit Sharing (401(k)) plan and/or the Company's Supplemental Deferred Compensation Plan. The information was obtained from the plan adminstrator as of a recent date. The number of shares is based on the account balance of the Company stock fund under the plan (which includes some money market instruments) divided by the market price of the Company's stock as of that date. /s/ William J. O'Shaughnessy, Jr., Attorney in Fact for Michael E. Prevoznik 2013-03-06