We compared the clinical and serological characteristics of 15 patients with onset of systemic lupus erythematosus after the age of 50 with those of 232 younger patients. The sex distribution was similar in both groups. All 15 patients were Caucasian. Autoimmune thyroiditis was found in 20% of the elderly patients. Initial manifestations, which presented more frequently in the older group, included thrombocytopenia (P < 0.05), sicca syndrome (P < 0.01) and cardiomyopathy (P < 0.005), whereas butterfly rash (P < 0.05) presented more frequently in the younger group. Analysis of cumulative clinical symptoms showed that butterfly rash (P < 0.05) and livedo reticularis (P < 0.05) were less frequent in the elderly. However, this group presented a significantly increased incidence of sicca syndrome (P < 0.005) and cardiomyopathy (P < 0.005). Antibodies to double-stranded DNA tended to occur less frequently in older patients (P < 0.05).