Associations between polymorphisms of DMA and DMB alleles and systemic lupus erythematosus (SLE) were studied in 51 Japanese SLE patients and 77 normal subjects by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Phenotype frequencies of DMB*0101 tended to increase in SLE, but the difference was not significant (76.5% vs 70.1% in controls). The phenotype frequency of DMB*0103 was decreased in the SLE group, but the difference was not significant (49.0% vs 53.2%). Furthermore, there was no evidence of any association of either DMA or DMB alleles with HLA-DRB1*1501. The phenotype frequency of DMB*0101 was higher in the SLE group with anti-double-stranded DNA antibody (a-dsDNA) than in the SLE group without a-dsDNA, but the difference was not significant (P = 0.045, corrected P not significant). No other DMA or DMB alleles showed any associations in various immunological subgroups of SLE. These data suggest that neither the DMA nor the DMB gene determines susceptibility to SLE in Japanese.