Genetic polymorphisms in HLA-A, -B, -C and -DR antigens were investigated in 78 unrelated Japanese patients with palmoplantar pustulosis (PPP) and compared with a total of 472 normal persons. Only HLA-DR9 showed a significantly increased frequency among all HLA antigens investigated (χ2 = 11.57, p < 0.001). It is suggested that major histocompatibility complex class II antigens including HLA-DR antigen may determine the susceptibility to PPP and PPP may be a distinct disease entity from psoriasis