Systemic lupus erythematosus (SLE) has a wide spectrum of laboratory findings and clinical manifestations. Our objective was to study the pleural/pulmonary involvement in patients with SLE. We have considered 200 patients, diagnosed according to ARA criteria for SLE. Patients were clinically examined, lab test (including immunology) of blood and pleural liquid were performed and also pulmonary biopsies were made. We found that pleurisy was the most frequent involvement, in 12% of patients. More than 50% of necropsies showed a pulmonary involvement; the most frequent aspect was of acute lupus pneumonia, with large hemorrhagic areas. Microscopy showed macrophages loaded with hemosiderin. The alveolar hemorrhage in SLE is due, possibly, to the impairment of coagulation and has a bad prognostic value.