Summary:Immunosuppressed oncology patients who develop pulmonary infiltrates during treatment have a mortality rate of the order of 55-90%. Early diagnosis and treatment is associated with increased survival. At present, diagnosis relies on invasive sampling of the respiratory tract using fibre-optic bronchoscopy. We have looked at a 30-month period, from June 1997 to December 1999, where 25 bronchoscopies were performed on patients from the Lymphoma and BMT units at The Royal Marsden Hospital for the further investigation of pulmonary infiltrates. Nine bronchoscopies (36%) yielded a positive result and seven (28%) led to a change in management. Analysis of the data showed that neither a positive result nor a change in management had any impact on overall survival. After reviewing the background literature on the investigation of pulmonary infiltrates in this group and discussion of the respective merits and limitations, we propose a management flowchart, with high-resolution computed tomography (HRCT) as the test arm in a future randomised trial of these patients. Bone Marrow Transplantation (2001) 27, 967-971. Keywords: oncology; HRCT; bronchoscopy The lung is a frequent site of infection in patients receiving treatment for malignancy. This occurs in up to 20% of cases and has a quoted mortality rate of 55-90%. 1,2 Although infection is the single most common cause of pulmonary infiltrates, a significant number are due to noninfective causes notably lung involvement with the primary malignancy, drug-related parenchymal disease, obliterative bronchiolitis, cryptogenic organising pneumonia (COP or BOOP), graft-versus-host disease and alveolar haemorrhage. The underlying pathogens are themselves dependent on the pattern of immunosuppression, as infections in patients with short bursts of neutropenia related to chemo-