The value of needle biopsy (NB) of pulmonary masses in patients unsuitable for surgery is well established. The presence of malignant cells confirms the diagnosis and thus aids management. We have reviewed 196 patients aged over 40 years with a solitary pulmonary mass suspected of being operable lung cancer to assess the effect of a negative NB result on the management. Malignant cells were discovered in 148 patients and diagnoses of infection were made in a further 10. In 38 patients no malignant cells were identified. Nineteen patients proceeded to thoracotomy and 13 of these had malignant disease. Nine others had further needle biopsies and eight of these had malignancy. Ten patients were followed up without any further intervention and four of these eventually proved to have malignancy. Thus of the 38 patients with no malignant cells on NB but no definite benign diagnosis, 25 had malignancy, six had benign disease and seven had presumed benign disease. In this series NB provided a definite benign diagnosis in 5.1% of patients. From this study it may be concluded that if a solitary pulmonary nodule has a high clinical suspicion of malignancy and the patient is a candidate for surgery, NB is of limited value in management.