Abstract Since the advent of the roentgenogram, very little information has appeared regarding the clinical significance of root resorption. Although microscopic studies revealed that most teeth show a small amount of resorption, the roentgenographic evidence of root resorption set up a heated controversy on the prognosis and surgical versus nonsurgical modalities of therapy. In the present article, pertinent quotations from the literature and cases illustrating the different types of external resorption accompany each of the subjects discussed according to the classification proposed by Shafer, Hine, and Levy