The incidence and characteristics of pulmonary haemorrhage in a series of 89 patients with systemic vasculitis were analysed. Pulmonary haemorrhage occurred in 32 of these patients and was associated with haemoptysis in all 32, alveolar shadowing in the chest radiograph in 28, and a significantly raised transfer coefficient in 30. Pulmonary haemorrhage usually resolved with treatment by immunosuppressive drugs but was the cause of death in 11 patients. In contrast with patients with antibasement membrane antibodies there was no correlation between pulmonary haemorrhage and cigarette smoking. Pulmonary haemorrhage is a cause of serious morbidity in patients with systemic vasculitis.