A randomized open study was undertaken to compare the therapeutic effects between low-dose etretinate alone and low-dose etretinate combined with eicosapentaenoic acid in 40 patients with chronic, stable psoriasis vulgaris. Better and more rapid improvement was obtained with the combination therapy for 12 weeks than with low-dose etretinate monotherapy. Eicosapentaenoic acid was safe, and adverse reactions due to low-dose etretinate were mild or tolerable. The combination regimen, therefore, has a satisfactory effect on psoriasis without marked adverse reactions.