Purpose: This study evaluated the etching effect of self-etching priming agents applied to intact and ground enamel. Materials and Methods: Thirty-two human molars were used. Each tooth was divided into two halves. The buccal or lingual mid-coronal surface of 32 half-teeth was ground with 600-grit silicon carbide paper. The other half-teeth were left intact (control). Teeth were treated with Clearfil SE Bond (SE), Prompt L-Pop (PLP) or Adper (AD). Those in the control group were etched with 35% phosphoric acid. The etching effect of such systems on enamel surfaces was assessed by three different approaches using scanning electron microscopy: 1) in situ or direct morphological examination of the etched enamel; 2) indirect morphological examination, that is, evaluation of the etching pattern left on resin reproductions; 3) adhesive interface examination. Results: SE exhibited the least aggressive dissolution of the intact and ground enamel, with many sites of the intact enamel remaining completely unetched. SE monomer infiltration into etched enamel was restricted to the superficial layer. PLP and AD produced equivalent etching patterns on intact and ground enamel, which resemble that produced by the phosphoric acid control group. PLP and AD monomer penetration extended along the porous subsurface enamel layer. Conclusion: SE produced mild morphological changes on intact and ground enamel surface, resulting in a very superficial resin infiltration particularly into intact enamel. No differences were evident among the etching and resin infiltration pattern produced by both all-in-one self-etching adhesives, PLP and AD, and the phosphoric acid system. Keywords: self-etching adhesives, enamel bonding, SEM evaluation