The bonding of a resinous sealant material to acid-etched sound human enamel was studied by means of a scanning electron microscope. Both the resinous bonding surfaces and the respective enamel surfaces of the specimens were exposed for inspection by dissolving one half of each specimen in hydrochloric acid so that only the resin matrix remained. Acid etching caused selective dissolution of the surface enamel so that, compared with the rod cores, more inter-prismatic substance was dissolved. The bonding surfaces of the resin material showed exact replication of the corresponding etched enamel. Tags of sealant, approximately 10 microns in length, were found on the acid-etched specimens.