The clinical and laboratory features of 18 males were compared with 254 female patients with systemic lupus erythematosus (SLE). At disease onset male patients were younger than female. Nephropathy, nephrotic syndrome and thrombocytopenia were significantly more frequent in male patients (p < 0.05). Pleuritis occurred as the initial symptom at a significantly higher frequency in males (p < 0.05). No significant immunological difference was found between two groups, except for anti-Sm antibodies which were more frequent in males than in females, but were measured in few patients. We concluded that male patients with SLE have a more severe disease, with higher morbidity, specially related to renal disease.