BETWEEN 12 and 18 months ago we treated three patients with FK S06 who had severe psoriasis that was refractory to conventionai therapy and four patients with w,despread incidental psonasis before undergoing hean or liver transplantation under FK 506. All had dramatic resolution of psonasis. which remaIned in remission as long as full-dose therapy was provided. Serial skin biopsies had a rapid disappearance of the inflammatory infiltrate and slower resolution 01 epidermal changes. FK 506 was well tolerated with onlv minor side effects during the 12 to 18 months of observation. Circumstantiai evidence for an autoimmune etiology of psoriasis is the striking remission of psonatic lesions. which can be achieved with cyclosporine. l l an immunosuppressive drug whose use for this pUJ'l)Ose has been limited by nephrotoxicity. hypenension. and other doserelated side effects. We repon here the use of the chemically unrelated drug. FK 506. which also inhibits T helper lymphocyte activation and the synthesis and expression of cytokines. 4.~