Chemotherapy-induced spontaneous pneumothorax (SP) has been described sporadically in chemosensitive tumors, particularly sarcoma, with multiple lung metastases. We present a patient who developed SP following rapid regression of bulky mediastinal lymphoma. Immediately on chest tube insertion, the lung recovered and further chemotherapy could be delivered uneventfully. We suggest that (1) chemotherapy-induced SP should be included amongst oncologic emergencies and that (2) a high degree of awareness of this complication is required.