Additions of ATP and inorganic phosphates to storage buffers, increase the viability of rat skin when stored at −196 °C and at −3 °C. The amino acid incorporation into the skin proteins, the α-[1- 14C]-aminoisobutyric acid uptake by the skin and to a lesser extend the [6- 3H]thymidine incorporation into DNA are protected by the phosphate compounds added to the storage medium. This stimulatory effect on the metabolic activity appears connected with the preservation and the protection of the oxidative phosphorylation, probably by providing the necessary phosphate radicals for the resynthesis of ATP. By simultaneously preventing potassium depletion during cooling and storage, the potassium phosphate compounds seem particularly suited to contribute to the preservation of the viability.