Popular forms of tooth bleaching are achieved in a variety of ways including office applied, office prescribed or over-the-counter treatments. Objective: This study was undertaken to test the hypothesis that bleaching agents of various forms will not affect microleakage composite restorations. Methods: Standardized Class V cavities were prepared on the buccal and lingual surfaces of 60 extracted human molars and filled with Scotchbond 1 and Filtek Z250 following the manufacturer's instructions. ). The teeth were randomly divided into 4 groups including a placebo control group PL, which was not bleached, (1) and 3 different bleaching procedures: in-office applied Opalescence Extra Boost (OPXB); in-office prescribed (with tray) Opalescence 20 % PF (OP20PF); and in office prescribed Crest Whitestrip Supreme (CWSS) whitening strips, respectively. Teeth were cycled in a regimen including a pre-test period (artificial saliva/pooled human saliva soaks with 2x/day NaF dentifrice treatment); test bleaching period (21 days, saliva + dentifrice treatment + bleaching exposure in cycles) and 7 days post bleach recovery (saliva + dentifrice treatment). Bleaching treatments were segmented to 0 hours for PL; 42 hours for CWSS, 42 hours for OP20PF and 45 minutes with OPXB. Nail varnish was applied to insulate non restored surfaces to dye prior to immersion in a 0.1% rhodamin-B-isothiocyanate for 24h at 37° C. After thorough rinsing with tap water the specimens were embedded in MA resin and sectioned with a water cooled microtome saw. Microleakage was evaluated at the coronal (enamel) and apical (dentin) restoration margins at 40x using a stereo microscope. Results: Microleakage (%) occurred in all groups as follows: (PL) 9, (CWWS) 9, (OP20PF) 5 and (OPXB) 8. Exact Kruskall-Wallis p values were determined for dentin = 0.57 and enamel = 0.91. Conclusion: Bleaching with various whitening treatments had no significant effect on microleakage of Class V composite restorations.