The effect of acid-etching on the surface topographies of caries-like lesions of enamel was studied using scanning electron microscopic techniques. The results indicated that etching patterns similar to those reported for etched sound enamel were observed when the lesions were etched with unbuffered phosphoric acid for 1 min. With a 30-second etching time, the surfaces of the lesions appeared to be fairly porous. With buffered etching solutions, surface coatings were found overlying the etched lesions. The acid-etch regimen used may allow placement of caries-resistant resins over initial lesions or aid in the remineralization process by producing an intact, porous surface zone that is more reactive.