Infections are one of the major causes of morbidity and mortality during the course of systemic lupus erythematosus, and are promoted by various dysfunctions of the immune system, some of which are poorly understood. Other predisposing factors have been also identified such as the presence of glomerulonephritis and a treatment with high-dose corticosteroids or immunosuppressors. These factors have been particularly associated with the occurrence of opportunistic infections such as systemic candidiasis or Pneumocystis carinii pneumonia, whose frequency has increased with the intensity of therapeutic strategies. The most frequent infections encountered are induced by community-acquired microorganisms. Thus, initiating an empirical antibiotic treatment is justified in febrile patients with lupus erythematosus. In case of marked lymphopenia, it is recommended to start cotrimoxazole as primary prophylaxis against P. carinii pneumonia.