In order to assess the value of computed tomography (CT) of the mediastinum, upper abdomen and head in the assessment of resectability of lung cancer, the CT findings of 262 patients, of whom 198 underwent thoracotomy, were analyzed retrospectively and the stagings obtained at CT and thoracotomy were compared. Mediastinal CT reliably predicted resectability when there was no evidence of mediastinal involvement. However, it was often impossible to determine whether tumour with apparent mediastinal infiltration on CT was resectable or not. The sole finding of lymph node enlargement did not permit differentiation of benign from malignant lymphadenopathy when the lymph node diameter was less than 25 mm and the lymphadenopathy was confined to one lymph node station. Upper abdominal metastases were found in 6.1% and brain metastases in 4.6% of patients and neither the histological type nor other features of the tumour were found to be useful predictors of their presence. The large number of non-specific findings decreased the utility of abdominal CT. The appropriate strategy for the pre-operative evaluation of patients with lung cancer is discussed.