We analysed the polymorphisms of HLA-DM genes in 85 unrelated Japanese patients with psoriasis vulgaris and 52 healthy controls using the polymerase chain reaction-restriction fragment length polymorphism method. The frequency of DMA*0101 was decreased (79% vs. 89%, P < 0.05) and that of DMA*0102 was increased (20% vs. 11%, P < 0.05) in the patients. However, neither of these remained significant after P-values were corrected for the number of comparisons made (Pc > 0.05). As we reported previously, HLA-C molecules are assumed to play a more important part than HLA-DM genes in the development of psoriasis vulgaris.