We studied the effects of products released from adhering neutrophils and serum factors from patients with psoriasis on angiogenic capability and natural cytotoxicity of normal human mononuclear cells. In active disseminated and guttate psoriasis, in which polymorphonuclear granulocytes were most adherent to the human vascular endothelium, supernatants from adhering neutrophils only slightly affected natural killer cell activity and angiogenic capability of normal human mononuclears. In peripherally spreading, plaque-like psoriasis, characterized by lower than in guttate psoriasis increase in granulocyte adherence, both neutrophil factors and patients sera markedly decreased NK cell activity and enhanced angiogenic capability of normal human peripheral blood mononuclear cells. The results suggest that neutrophil factors may affect some immune responses in patients with psoriasis.