Although cortisol slightly inhibited the incorporation of 2-14C]glycine into the proteins of rat skin samples incubated in vitro, addition of the hormone to the storage medium had a marked protective effect on protein and DNA metabolism. The incorporation of [2-14C]glycine into the proteins, and to a lesser degree that of [6-3H]thymidine into DNA, were stimulated when the incubated skin had been exposed to cortisol during storage. The skin samples stored in buffer containing cortisol transported α-aminoisobutyric acid more effectively; this was concluded to be due to a stabilizing effect of cortisol on the cell membrane. During storage protein catabolism and possibly protein turnover were stimulated by cortisol.