Abstract Thirty-eight pairs of premolars, extracted for orthodontic reasons, were tested for the effects of various pretreatment methods of the enamel in bonding procedures. Etched enamel surfaces and inner bracket surfaces facing the etched enamel were studied with the scanning electron microscope. The results were based on a pair-by-pair evaluation of 650 photographs. The degree of surface irregularities indicating the quality of microretentions was evaluated. A scale from 0 to 3 was used; 0 represented a smooth surface, and 3 represented optimum irregularities. Scores for bracket inner surfaces were always higher than those for corresponding etched enamel surfaces. Future SEM comparative investigations, therefore, ought to be based on replicas of etched enamel surfaces. One-minute etching with an acid gel had the same effect as etching with an acid liquid for the same time. Furthermore, mechanical pretreatment procedures, such as diamond grinding and aluminum oxide grinding, as opposed to pumicing did not improve the effect of the acid. Chemical pretreatment of the enamel with organic solvents such as 8 to 12 percent sodium hypochlorite did not improve the effect of the acid. Fluoride pretreatment with a fluoride varnish. Duraphat, did not have any negative effect on the etching results.