OBJECTIVE: Small Japanese studies have suggested that patients with schizophrenia have higher rates of the HLA-DR1 gene than normal subjects. The authors’ goal in the present study was to confirm this finding in a larger number of Japanese subjects. They also investigated the rate of DR4 in Japanese patients with schizophrenia because it has been reported that Caucasian patients with schizophrenia have higher rates of DR4. METHOD: They studied the occurrence of the HLA-DRB1 gene in 233 unrelated Japanese patients with schizophrenia compared with the occurrence of the gene in a group of 493 healthy Japanese volunteers. RESULTS: A larger proportion of the patients with schizophrenia (15.9%) than the comparison subjects (10.5%) were found to have DR1 (DRB1*0101). The proportion of patients (36.9%) and comparison subjects (40.6%) with DR4 did not differ significantly. CONCLUSIONS: Consistent with the findings of three other Japanese studies, the findings of the present study suggest that the rate of HLA-DR1 may be higher in Japanese patients with schizophrenia than in normal Japanese subjects. No evidence for an association between schizophrenia and the rate of DR4 was obtained in this study, although the combined data from the present study and other Japanese studies support the finding of lower rates of DR4 among patients with schizophrenia.