Recently, there has been a tendency to simplify bonding procedures. Current self-etching adhesives combine conditioning, priming and bonding functions thus reducing technique-sensitivity as well as the risk of making errors. Another important advantage of this approach is that it allows the resin to etch and infiltrate the substratum simultaneously thus reducing the risk of any discrepancy between these 2 processes. The aim of this study was to evaluate the bonding quality of 4 self-etching adhesives both on dentin and enamel using SEM analysis.Twenty caries-free molars were used. The aprismatic enamel layer was removed from the internal and external slopes of the vestibular cusps using a diamond bur. Each molar was then transversally cut just above the pulp chamber using a diamond saw (composhave 4255 Intensiv) thus obtaining twenty coronal fragments and 20 radicular fragments. Radicular and coronal fragments were then randomly divided into 5 groups. Each group consisted of 8 specimens: 4 coronal and 4 radicular ones. A different adhesive system was used for each group following the manufacturer's directions. Each group underwent the same treatment: a thin layer of flowable composite was applied and then polymerized. Subsequently, a single 2 mm layer of microhybrid composite was added. The coronal and radicular portions were longitudinally cut to show the ground enamel/adhesive, unground enamel/adhesive and dentine/adhesive interfaces. Eighty specimens were obtained and prepared for SEM observation. Forty specimens with an adhesive/enamel interface and 40 with an adhesive/dentine interface.The interfacial exam frequently showed gaps between the substratum and the restoration. The final etching was generally satisfactory on ground enamel, while it was poor on unground enamel. Sometimes gaps were evident at the adhesive interface in dentin specimens. The tested adhesive systems produced a suitable hybrid layer and a lot of resin-tags were present.Self-etching adhesives showed an adequate adhesion to dentin. However, while they provided encouraging results on ground enamel they did not show to be dependable on unground enamel.