An open study testing the effects of fish oil supplementation on psoriasis in 26 patients is described. None of the patients with plaque-type psoriasis vulgaris showed clinically significant improvement; however, a patient with generalized pustular psoriasis showed marked improvement with the fish oil supplementation. In this patient, scale leukotriene B4 levels were determined and shown to be significantly decreased after completion of the study, but the leukotriene B4 levels did not correlate with her clinical course. The results of our study are contrasted with those of a recent study that did show beneficial effects of fish oil supplementation on plaque-type psoriasis.