To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layer's morphology. Four one-bottle etch-and-rinse adhesive systems containing different solvents-Group A: Scotchbond 1XT (TM) - 3M ESPE, Group B: XP - Bond (TM) - Dentsply, Group C: Prime&Bond NT (R) - Dentply, and Group D: One Coat Bond (R) - Coltene Whaledent-were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used. The hybrid layer thickness average found was 3.23 mu m (+/- 0.53) in Group A, 3.13 mu m (+/- 0.73) in Group B, 2.53 mu m (+/- 0.50) in Group C, and 1.84 mu m (+/- 0.27) in Group D. Prime&Bond NT (R) presented a more inconsistent hybrid layer. The solvent seems to play a significant role in hybrid layer structure and thickness.