Purpose: To determine the shear bond strength to dentin of five newer-generation selfetching adhesive systems. Method and materials: Flat bonding sites were prepared on 100 extracted human molar teeth with 600-grit silicon carbide paper, which exposed the dentin. The systems tested were: Clearfil SE Bond; Optibond Solo Plus Self-Etch; Xeno CF III; Tyrian SPE; and Adper Prompt L-Pop. Following application of each adhesive system, bonded assemblies of Z-100 were prepared using a gelatin capsule matrix (n = 20). Ten specimens in each group were debonded after water storage for 24 hours at 37°C, and 10 were stored for at least 30 days, followed by thermocycling for 850 cycles between water baths at 5°C and 55°C, with a dwell time of 1 minute in each bath. Specimens were loaded to failure in an Instron Model 1123 testing machine with a crosshead speed of 5 mm/min. Statistical analysis included a two-way analysis of variance (adhesive and time) and Tukey's post hoc test. Results: Mean shear bond strengths (MPa) at 24 hours were: Clearfil, 26.4 ± 4.2; Optibond, 23.5 ± 4.4; Xeno, 19.5 ± 4.2; Tyrian, 16.5 ± 3.7; and Adper, 15.3 ± 3.3. Mean shear bond strengths (MPa) after storage and thermocycling were: Optibond, 27.5 ± 5.7; Clearfil, 25.5 ± 4.9; Adper, 21.5 ± 3.3; Xeno, 20.4 ± 2.2; and Tyrian, 19.2 ± 6.4. Both adhesive system and storage time were significant factors affecting shear bond strength (P .05). Conclusion: There are significant differences in the in vitro dentin shear bond strength among the self-etching adhesive materials tested. Water storage and thermocycling did not significantly degrade the shear bond strength of the materials in this study. Keywords: adhesive systems, dentin bonding, dentin smear layer, postoperative sensitivity, self-etching adhesives, shear bond strength