The psoriasis plaque test, as a clinical and non-artificial model, provides information on the antiproliferative effect of topical corticosteroids, and it makes possible to ealuate various preparations simultaneously at a given time. In this assay we compared the antiproliferative effects of six topical corticosteroids with occlusive dressing technique in fourteen psoriatic patients. The results are summerized as follows : 1) The psoriasis plaque test was an adequate method for evaluating antiproliferative effects of various corticosteroid preparations. 2) In contrast to prednisolone and triamcinolone acetonide, the effects of desoxymethasone, halcinonide, fluocinide, triamcinolone benetonide were evident, and the best of all was desoxymethasone. 3) No side effect developed during test period.