Fifty chest radiographs and concurrent thoracic computed tomography (CT) scans obtained in a total of 44 patients with 50 separate episodes of suspected recurrent Hodgkin's disease were reviewed. Recurrent disease was present in 18 episodes, involving the mediastinum in 12, the lung parenchyma in five and both mediastinum and lung parenchyma in one. In four episodes, mediastinal recurrence was demonstrated on both the chest radiograph and CT scan. In a further two cases, the chest radiograph appeared normal but CT detected recurrence in the mediastinum. In 20 cases, the mediastinal appearances on chest radiography were suspicious but not diagnostic of recurrence, usually because of previous radiotherapy resulting in residual mediastinal widening. Computed tomography diagnosed recurrent disease which was subsequently proven in seven of these cases. Recurrent disease was suggested by CT in a further case, subsequently shown to be radiation fibrosis. Of the 12 remaining chest radiographs in which the mediastinal assessment was indeterminate, CT was true negative for recurrent disease in 10 cases and was also indeterminate in two. Recurrent disease in the lung parenchyma was demonstrated on the chest radiograph and CT scan on five occasions. There was one incident in which the chest radiograph was normal but CT detected recurrent parenchymal disease. The appearances of the lung parenchyma were indeterminate for recurrent disease on three chest radiographs but CT was helpful in only one case in which radiation change alone was diagnosed. In eight cases the diagnosis of recurrent disease by CT resulted in a decision to initiate treatment. Computed tomography is of value in detecting relapse in patients with suspected recurrent Hodgkin's disease when the chest radiograph is inconclusive, and may enable differentiation of radiation change from recurrent disease in the mediastinum.