Taglike projections of resin into the etched enamel surface and longitudinally cut enamel were studied under the SEM. Three methods of bonding, including the use of a bonding agent and a primer, were compared. Freshly extracted teeth were pumiced, rinsed, and dried. The enamel surface was etched for a minute with phosphoric acid. Adaptic with bonding agent, Simulate with primer, and Simulate without primer were then applied to the etched enamel. After the teeth were sectioned, the enamel was etched with phosphoric acid and viewed under the SEM. The resin projections into the etched rod ends at the enamel surface were 5 to 10 mu in length, with similar cuplike and coneline patterns of tags for the three methods of bonding. Troughlike and ridgelike projections into the longitudinally cut enamel were 3 to 5 mu in length; patterns of tags were similar for the three bonding methods. No observable differences in length and pattern of tags were noticed among the three bonding methods.