Carmustine (BCNU) is a cytotoxic drug which is a recognized cause of acute pulmonary fibrosis. We describe the radiological findings in six patients who received carmustine in childhood for treatment of central nervous system tumours and were subsequently found to have pulmonary fibrosis 13-17 years after treatment. Patients were studied by chest radiography and high resolution computed tomography. The pattern of disease is novel, involving the upper zones in a predominantly peripheral pattern. © 1991 The Royal College of Radiologists. All rights reserved.