The purpose of the present study was to explore the possibility of obtaining an acceptable smear-removing and collagen-exposing effect following EDTA etching with concentrations lower than supersaturation (24%). A flat dentin surface was created on human teeth extracted due to severe periodontitis. The teeth were etched with the following concentrations of EDTA for 2 min: 1.5% (group I), 5% (group II), 15% (group III) and 24% (group IV), and evaluated with scanning electron microscopy with respect to smear layer removal and exposure of root-associated collagen fibers. It was found that neither 1.5% nor 5% EDTA etching was sufficient to dissolve the smear layer to any higher degree. Etching with 15% EDTA dissolved the smear more effectively than the lower concentrations and collagen fibers were sparsely found. Following etching with 24% EDTA (group IV), significantly less smear was seen on the dentin surfaces than in any of the other groups and collagen fibers were seen covering the entire intertubular dentin surfaces. Based on these findings, the concentration of EDTA should be somewhere between 15 to 24% in order to obtain an acceptable smear removing and collagen-exposing effect within a clinically acceptable time period.