Objective: To study the sealing ability of a self-adhesive sealant. Method and Materials: Thirty-five extracted molars were assigned to seven groups: group 1, 35% phosphoric acid (PA) followed by Clinpro Sealant (CL) as the control group; group 2, Enamel Loc (EL), a self-adhesive sealant; group 3, PA followed by EL; group 4, Adper Prompt L-Pop (AP) followed by CL; group 5, AP followed by EL; group 6, PA followed by Adper Single Bond Plus (SB) and CL; and group 7, PA followed by SB and EL. Specimens were thermocycled and immersed in 50 wt% ammoniac silver nitrate. Silver leakage was measured in ranks from 0 to 4 and analyzed with Kruskal-Wallis and Mann-Whitney tests at P .05. One additional tooth per group was used to study the enamel etching pattern. Specimens were observed under a field-emission SEM. Results: The least silver infiltration was measured for group 1 (control group), which was significantly different from all other six groups. Etching enamel prior to the application of EL resulted in significantly less leakage than all other groups, except for the control group. EL alone resulted in similar leakage to EL with either AP or SB. None of the groups resulted in perfectly sealed interfaces. Under SEM, EL was unable to etch enamel. The self-etch adhesive AP resulted in a less defined etching pattern than the etch-and-rinse adhesive SB. Conclusion: Etching enamel with phosphoric acid is still essential for sealing the enamel-sealant interface. The self-adhesive sealant tested in this study may not be indicated for clinical use. Keywords: dental bonding, dental leakage, electron microscopy, enamel etching, pit and fissure sealant