The possibility that products released by inflammatory cells may play a role in the induction/maintenance of psoriasis is suggested by the observation that psoriasis, a disease of excess epidermal proliferation, is linked to inflammatory events. As an assessment of this possibility, the effects of supernatants from antigen stimulated and unstimulated peripheral blood mononuclear cells from normal and psoriatic subjects on the proliferation of HeLa cell cultures are presented. Data demonstrate that supernatants contain factors which both inhibit and enhance cell proliferation, both of which are released in greater quantities from antigen stimulated peripheral blood mononuclear cells. Dilutional and pulsing experiments show that proliferation enhancing factors present in these supernatants have an apparent greater affinity for HeLa cells than does the inhibitory component. Relative to HeLa cell proliferation in fresh media, both antigen stimulated and control supernatants from peripheral blood mononuclear cells of subjects with psoriasis have significantly less inhibitory and more of the enhancing effect than similar supernatants from normal subjects. Individual, as well as pooled, supernatants from subjects with psoriasis demonstrate these differences. The kinetics of this response are the same, normal vs. psoriasis. This "net effect" of supernatants from patients with psoriasis favoring proliferation is in harmony with the concept of inflammatory events playing a role in cell proliferation, and may be important in the induction/maintenance of psoriasis.