A ball-valve airway obstruction by a blood clot cast of almost the whole bronchial tree occurred in a small-cell lung cancer patient, who had been on mechanical ventilation for 9 days. Chest radiographs revealed overinflated lungs. Attempts to remove the cast via fibreoptic bronchoscopy were unsuccessful and the patient died. A postmortem extraction of the clot was performed with a rigid tube. This case is rare because of absence of severe haemoptysis and lung volume reduction.