Psoriasis represents a source of distress and disability to approximately 2 percent of the population of the United States, yet the etiology of the accelerated rate of epidermal cell proliferation that is responsible for the lesions of the disease remains unknown. This process raises questions that are fundamental in cell biology, and analytical investigative approaches have utilized increasingly penetrating studies of the basic biology of epidermal cells and of the nature of cellular growth control. Current investigations have included detailed analyses of photobiological, immunological and chemical parameters of the disease process. Two previous international Symposia have been held (in 1971 and 1976); these were highly successful in spreading information and in initiating discussion among scientists from 30 different countries. The ensuing five years have seen an increasing tempo of research, justifying another symposium, in which, because of the increasing attention to fundamental aspects of epidermal cell biolgoy, special participation by authorities in appropriate areas of basic cell biology will contribute prominently to the program. There is no completely satisfactory method of treating psoriasis, but a variety of procedures can cause regression or modification of the lesions. Careful analysis of these should add substantially to the understanding of the disease process. Thus the actions of effective therapeutic agents will be examined during the symposium. The Third International Symposium on Psoriasis will be held at Stanford University from July 13 to 17, 1981.