HLA-DR antigens were tested in 38 Caucasian, 18 Negro, 17 Mexican and 5 Japanese patients with rheumatoid arthritis. Significantly high HLA-DR4 frequencies were observed in all races: 61% in Caucasians, 39% in Negroes, 77% in Mexicans and 100% in Japanese. No clinical correlation with DR4 was found in these patients.