Anti-myosin antibodies (AMA) in the sera of patients with systemic lupus erythematosus (SLE) and healthy subjects were measured by ELISA. AMA were IgM dominant. The titers of AMA were significantly higher in active SLE than in inactive SLE and healthy subjects. AMA negative SLE patients have significantly lower serum IgM than that in AMA positive subjects. Frequency analysis of HLA antigens in SLE revealed that AMA positivity was associated with HLA-A11, AMA negativity with HLA-B40 and DR2, and those with central nervous system involvement (CNS-SLE) were associated with HLA-B40. The patients with CNS-SLE have low serum IgM, low titer of AMA and HLA-B40.