Five hundred and seventy patients with systemic lupus erythematosus were classified into 3 groups (younger onset, adult onset and older onset) according to their ages at the time of diagnosis. There were more patients with HLA-Bw35 and/or DR2 in the younger onset group than the adult onset group. Typically related systemic features and serological abnormalities were more frequently found in the younger onset group than the other groups. The disease patterns of the adult onset group were more heterogeneous than those of the other 2 groups. The causes of death in the older onset group were mainly complications such as infections and perforated peptic ulcers.