Seven patients with fibrosing alveolitis who failed to respond to prednisolone and cyclophosphamide and were deteriorating, were treated with cyclosporin A. An initial favourable response was seen but was not maintained. When compared to a control population, matched for the extremely severe disease present in the treated group, survival was doubled from 2.5 to 5 months. With growing awareness of the possibility of heart-lung transplantation in this disease, even this trivial increase in survival may be of crucial importance in individual patients.