The purpose of this study was to observe the effectiveness of EDTA and ethylenediamine mixtures in removing the smear layer from prepared root canal walls following instrumentation. Thirty-five freshly extracted, single-rooted maxillary anterior teeth were used. After the preparation of access cavities and establishing the working length, the apical foramen of each canal was sealed with casting wax. All canals were then sequentially enlarged with K-type files to size 50. The sample was divided into seven groups of five teeth. The teeth in the control group were irrigated with saline solution. The specimens in the other groups were irrigated with 10 and 20 ml of three different EDTA-ethylenediamine mixtures. A scanning electron microscopic evaluation of the canal walls following irrigation showed that the superficial layer was totally removed and the openings of the dentinal tubules were patent. Only at the coronal third of the teeth in group 4 and the apical thirds in groups 2 and 4 was a moderate smear layer observed. The most favorable results were obtained with groups 5, 6, and 7. The results show that the smear layer can be totally removed by using 10 ml of a four-to-three by volume mixture of EDTA and ethylenediamine for irrigation of instrumented root canals.