Purpose: The objective of this project was to compare the microtensile bond strengths (µTBS) of five "all-in-one" adhesives using two 2-step adhesives as controls. Materials and Methods: Eighty-four extracted human molars were randomly assigned to one of three substrates: dentin, unground enamel, or ground enamel. For each substrate, specimens were randomly assigned to one of five allin- one adhesives: (1) Adper Prompt L-Pop (AP, 3M ESPE); (2) Clearfil S3 Bond (S3, Kuraray); (3) G-Bond (GB, GC America) (4) iBond (iB, Heraeus Kulzer); (5) Xeno IV (XE, Dentsply Caulk). Adper Single Bond Plus (SB, 3M ESPE) was used as a two-step etch-and-rinse control, while Clearfil SE Bond (SE, Kuraray) was used as a two-step self-etching control. Crowns were built with Filtek Z250 (3M ESPE) and sectioned in x and y directions. The resulting sticks were fractured in tension at a crosshead speed of 1 mm/min. Statistical analysis was computed for each substrate with one-way ANOVA and Duncan's post-hoc test at p 0.05. Results: Means ± SD are given in MPa; pretesting failures are shown in brackets. Dentin - SE: 79.1 ± 20.5, [0/85]; SB: 76.3 ± 19.3, [0/82]; AP: 51.6 ± 21.9, [0/90]; XE: 40.5 ± 22.9, [7/81]; S3: 27.8 ± 13.2, [7/91]; iB: 17.4 ± 15.6, [25/91]; GB: 11.7 ± 7.4, [5/92]. Unground enamel - SB: 33.1 ± 10.5, [0/69]; AP: 27.6 ± 7.5, [0/66]; S3: 24.6 ± 12.0, [0/70]; SE: 16.8 ± 11.7, [3/60]; XE 15.4 ± 14.1, [16/63]; iB: 11.2 ± 11.5, [18/64]; GB: 9.5 ± 12.4, [31/63]. Ground enamel - SB: 33.7 ± 9.1, [0/69]; AP: 33.2 ± 7.9, [0/77]; SE: 26.4 ± 9.5, [0/67]; S3: 25.5 ± 8.9; [0/56]; XE: 21.0 ± 8.9, [3/68]; GB: 18.2 ± 10.3, [4/68]; iB: 12.3 ± 8.9, [11/52]. For dentin, the Duncan's test ranked the means in 6 statistical subsets: GB Keywords: dental adhesion, acid etching, bond strength testing