The bronchial scrubbing method under artificial pneumothorax technique was studied as the diagnostic method for the bronchoscopically invisible lung cancer . 17 of 20 lung cancer cases (85%) were cytologically positive, 9 of these 17 cases were positive only by this method.Many lung cancer cases restricted the stenotic or obstructive movement of bronchi seen at the time of lung collapse.The scrubbing brush is easily inserted into the lesioned bronchus under this condition.