The aim of this study was to investigate tooth whitening efficacy and oral side effects during bleaching with Whitestrips (WS) (6% hydrogen peroxide H(2)O(2) gel) and Vivadent Vivastyle (VS) (10% carbamide peroxide gel). Forty-seven subjects were included in this single blind, randomized, parallel group study. Application of WS was performed twice a day for 30 min. Trays filled with VS were worn for 60 min once a day. Tooth color was evaluated by measuring L*a*b* values before the study and after completion of the bleaching. Treatment tolerability was monitored throughout bleaching with an 8-week follow-up after completion of therapy. After 2 weeks both treatment groups demonstrated significant improvements in tooth color compared to baseline. A shift toward less yellow (-Deltab) and brighter (+DeltaL) tooth color was observed. Deltab amounted to -1.69 +/- 0.38 for WS and -1.20 +/- 0.34 for VS (mean value +/- SE). DeltaL was +1.55 +/- 0.41 for WS and +1.20 +/- 0.37 for VS. There was no significant difference between the two systems. No significant differences between the two bleaching systems were recorded for clinically observed signs or reported symptoms. Gingival irritation was observed in 13%, reported tooth hypersensitivities in 22% and reported gum irritation in 20% of the total study population. At an 8-week follow-up visit no adverse effects were observed. Both WS and VS demonstrated significant and comparable levels of tooth color improvement after 2 weeks. Each treatment caused similar levels of transient oral side effects.