SUMMARYThe survival time of grafts exchanged between BALB/c and C57BL/6 mice was significantly prolonged nearly twice that of untreated controls by topical application of triamcinolone acetonide prior to transplantation. A study of the mechanism of this prolongation, using mice and rabbits, suggests a dualistic action of topically applied corticosteroid. Evidence presented shows that local steroid both retards the devlopment of immunity toward skin allografts and suppresses the local inflammatory response in the immunized animal.