To evaluate the effect of dentin pretreatment with 2.5% titanium tetrafluoride (TiF4) on microtensile bond strength (microTBS) of one- or two-step self-etching adhesive systems. 24 human sound third molars were used. A flat dentin surface of each tooth was exposed. After planing, teeth were divided into groups so that dentin would be left untreated or treated with a 2.5% TiF4 solution for 1 minute. Specimens were then subdivided into two groups to receive one of the following adhesive systems: one-step self-etching Adper Easy One (ADP) or two-step self-etching adhesive Clearfil SE Bond (CLEAR). A block of composite measuring 5.0 mm high and 5.0 mm wide was made incrementally on the tooth. Specimens were taken to a metallographic cutter to fabricate sticks with a bond area of approximately 1 mm2. After 24 hours, specimens were submitted to microTBS testing and the failure mode was recorded by examining specimens under stereomicroscopy. Scanning electron microscope (SEM) photomicrographs were obtained of the tooth/restoration interface. Two-way ANOVA and Tukey's test demonstrated that pretreatment of dentin with a TiF4 solution did not affect the microTBS values of either of the adhesive systems (P = 0.675). CLEAR provided higher bond strength than ADP, regardless of whether dentin was or was not pretreated with the TiF4 solution. Failure mode showed mostly adhesive failures in all groups, except when only ADP was used, causing mostly cohesive fractures in resin.