Soluble solutions of psoriasis scale were prepared by extracting scales in 6 M urea and removing urea by dialysis. Extracts were tested for chemokinetic and chemotactic activity for human polymorphonuclear leukocytes and mononuclear cells in vitro using the migration under agarose assay. Five of 6 extracts demonstrated significant chemotactic activity for polymorphonuclear leukocytes, and 4 of 6 were also chemotactic for mononuclear cells. All extracts augmented random migration of polymorphonuclear leukocytes (chemokinesis). Checkerboard experiments showed extracts were truly chemotactic as well as chemokinetic. The kinetics of polymorphonuclear leukocyte and mononuclear cell chemotaxis toward psoriasis scale extracts were similar to kinetics of chemotaxis toward a bacteria-derived chemotactic factor and zymosan-activated serum. Since zymosan-activated serum and purified C5a were not chemokinetic, psoriasis scale extract was more like a bacteria-culture supernate than these complement factors in augmenting random migration of polymorphonuclear leukocytes. Substances in psoriasis scale may be capable of influencing the inflammatory response.