Chemokinesis and chemotaxis of neutrophil leucocytes were studied by migration under agarose in 35 patients with psoriasis and compared with 35 healthy controls. Eschericheae coli filtrate and lipopolysaccharide were used as chemo-attractants. Of these patients, 14 were tested before and after photochemotherapy. The chemotactic capacities of psoriatic serum before and after PUVA therapy were also investigated. The increase in the chemotactic activity of psoriatic polymorphonuclear leucocytes (PMNs) was not significant and remained unchanged after PUVA therapy. The activated psoriatic serum showed a slight increase in chemotactic activity when compared with normal activated serum. These results do not support an intrinsic abnormality of psoriatic PMNs, and their migration into psoriatic lesions could be chiefly due to the presence of chemotactic factors in involved epidermis.