Infection has now become the most frequent cause of death in systemic lupus erythematosus. Seven patients were seen in a 4 year period who developed infections requiring admission to hospital. Severe infections generally occurred early in the course of the disease. Despite intensive antibiotic therapy only 3 patients survived. Death was associated with corticosteroid dosage, azathioprine therapy, the severity of anaemia, and with the occurrence of septicaemia. In this study neither the occurrence of infection nor a fatal outcome were associated with features of active disease. It is concluded that patients with systemic lupus need regular monitoring, even when disease is well controlled, so as to minimise dosages of corticosteroids and immunosuppressive drugs and prevent the occurrence of fatal infections.