To investigate the effect of high frequency ultrasonic agitation on the microtensile bond strengths of different self-etching adhesives.Thirty-six human molars were wet ground occlusally until dentin was exposed. The one-step self-etching adhesives Clearfil S3 Bond, G-Bond, and Futurabond NR were tested in this study. In the control groups, bonding procedures were performed according to the manufacturers' instructions. In the experimental groups, bonding materials were applied with a 1 MHz therapeutic ultrasonic device on the dentin surfaces. The composite crown was built up incrementally to a height of 5 mm. Each tooth was serially sectioned into rectangular beams, and the specimens were subjected to microtensile testing. Failure modes were observed under a stereomicroscope and classified. Randomly selected specimens from each group were observed with SEM.Two-factor ANOVA indicated that both the adhesive system and the ultrasonic agitation effect influenced bond strength (p0.05). The bond strength of G-Bond adhesive to dentin was higher after ultrasonic agitation (p0.05), whereas ultrasonic agitation of Futurabond and S3 Bond did not affect bond strength values (p0.05). Failure after the test was commonly due to adhesive failure in the dentin.High-frequency ultrasonic agitation of self-etching adhesives during their application may enhance their bonding performance.