OBJECTIVE: The purpose of this study was to evaluate the resin infiltration into dentin of one-bottle adhesive systems and self-etching primer bonded to Class V cavities using confocal laser scanning microscope(CLSM). MATERIAL AND METHODS: Forty Class V cavities were prepared from freshly extracted caries-free human teeth. These teeth were divided into two groups based on the presence of cervical abrasion: Group I, cervical abrasion; Group II, wedge-shaped cavity preparation. Resin-dentin interfaces were produced with two one-bottle dentin bonding systems-ONE COAT BOND(OCB; Coltene(R)) and Syntac(R)Srint(TM)(SS; VIVADENT)-, one self-etching priming system-CLEARFIL(TM) SE BOND(SB; KURARAY)- and one multi-step dentin bonding system-Scotchbond(TM)Multi-Purpose(SBMP, 3M Dental Products)-as control according to manufacturers'instructions. Cavities were restored with Spectrum(R)(Dentsply). Specimens were immersed in saline for 24 hours and sectioned longitudinally with a low-speed diamond disc. The resin-dentin interfaces were microscopically observed using CLSM. The quality of resin-infiltrated dentin layers were evaluated by five dentists using 0-4 scale. RESULTS: Confocal laser scanning microscopal investigations using primer labeled with rhodamine B showed that the penetration of the primer occurred along the cavity margins. Statistical analysis using one-way ANOVA followed by Duncan's Multiple Range test revealed that the primer penetration of the group 2(wedge-shaped cavity preparation) was more effective than group 1(cervical abrasion) and that of the gingival interfaces was more effective than the occlusal interfaces. In the one-bottle dentin bonding systems, the resin penetration score of OCB was compatible to SBMP, but those of SS and self-etching priming system, SB were lower than SBMP.