This study presents a retrospective review of chest radiography in children with Murphy stage III T-cell lymphoblastic lymphoma. All received a standard leukaemia-based protocol with intensive induction, consolidation and continuing chemotherapy. Neither initial thoracic disease bulk nor the presence of a pleural effusion predicted outcome. However a significant difference was found when the 50 patients in whom the chest radiograph returned to normal within 60 days of commencing treatment were compared with the 18 patients with persistent mediastinal abnormalities, for both event-free [hazard ratio < or = 60 days to > 60 days (HR) 3.55 (95% CI 1.33-9.48); P = 0.007] and overall survival [HR 2.95 (95% CI 1.07-8.18); P = 0.03]. It appears that this relatively simple estimate of chemosensitivity may identify a group of particularly good-risk patients in whom drugs associated with late morbidity such as anthracyclines may be reduced and conversely a higher risk group in whom further intensification of treatment would be justified.