Purpose: To evaluate the microtensile bond strength (µTBS) of two all-in-one self-etching adhesive systems and two selfetching adhesives with and without simulated hydrostatic pulpal pressure (PP). Materials and Methods: Flat coronal dentin surfaces of extracted human molars were prepared. Two all-in-one self-etching adhesive systems, One-Up Bond F (OBF; Tokuyama) and Clearfil S3 Bond (Tri-S, Kuraray Medical) and two self-etching primer adhesives, Clearfil Protect Bond (PB; Kuraray) and Clearfil SE Bond (SE; Kuraray) were applied to the dentin surfaces according to manufacturers' instructions under either a pulpal pressure (PP) of zero or 15 cm H2O. A hybrid resin composite (Clearfil AP-X, Kuraray) was used for the coronal buildup. Specimens bonded under PP were stored in water at 37°C under 15 cm H2O for 24 h. Specimens not bonded under PP were stored under a PP of zero. After storage, the bonded specimens were sectioned into slabs that were trimmed to hourglass-shaped specimens, and were subjected to microtensile bond testing (µTBS). The bond strength data were statistically analyzed using two-way ANOVA and the Holm-Sidak method for multiple comparison tests (α = 0.05). The surface area percentage of different failure modes for each material was also statistically analyzed with three one-way ANOVAs and Tukey's multiple comparison tests. Results: The µTBS of OBF and Tri-S fell significantly under PP. However, in the PB and SE bonded specimens under PP, there were no significant differences compared with the control groups without PP. Conclusions: The µTBS of the two all-in-one adhesive systems decreased when PP was applied. However, the µTBS of both self-etching primer adhesives did not decrease under PP. Palabras clave: dentin, pulpal pressure, all-in-one adhesives, microtensile bond strength