Dermabrasion with freezing anesthesia induced by ethyl chloride or other refrigerants has been used extensively since Kurtin1perfected this form of therapy.*Two particular problems are the subject of this paper: (1) the regenerative processes following dermabrasion and (2) the limits of safety, especially in respect to (a) the duration and depth of freezing, (b) the depth of planing, and (c) the formation of hypertrophic scars and keloids. All of the experimental subjects were adult male prisoners, mostly Negroes. Freezing Experiments Dermatologists are naturally fearful of producing irreversible tissue damage by freezing. Though there is no experimental work on which to base opinions, injunctions against refreezing an area have already been issued,4and it is quite likely that most practitioners of the technique work under the strain of producing the quickest and lightest type of freezing for the shortest period of time