Objective: The purpose of this study was to compare the seal along dentin and enamel margins produced by 3 self-etching resin bonding systems to that of an etch-and-rinse adhesive system. Potential improvement in adaptation along enamel margins through the experimental use of conventional enamel etching prior to application of the self-etching adhesives was also evaluated. Method and materials: Class V resin composite restorations were placed in prepared cavities in extracted third molars using 3 self-etching dentin adhesive systems: Adper Prompt L-Pop (3M Espe), iBond GI (Heraeus Kulzer), and Tyrian SPE (Bisco), and an etch-and-rinse adhesive, Adper ScotchBond Multi-Purpose (3M Espe). A group of teeth also underwent conventional enamel etching prior to use of the self-etching products. The restored teeth were thermocycled, subjected to a dye challenge, and sectioned. The sections were scored using an ordinal leakage scale (n = 20). Ranked data were analyzed using a 2-way analysis of variance and Tukey multiple comparison. Results: When used as directed, there were no significant differences along dentin margins for any of the adhesives, but Adper Prompt and iBond demonstrated significantly greater leakage than the etch-and-rinse product along enamel margins. The incidence of enamel margin leakage decreased significantly for the same 2 products when enamel etching preceded use of the resin. Enamel etching increased the leakage along dentin margins for all 3 self-etching products, but not significantly. Conclusion: Considerable improvement of all classes of dentin-adhesive resin systems is still needed. Practitioners should await further clinical trials before adopting use of self-etching resins, especially for large occlusal restorations. Schlagwörter: dentin adhesion, enamel adhesion, microleakage, resin composite, self-etching resin