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.