Description of a method to obtain by thoracoscopy adequate material for different investigation - purposes, in behalf of the pathologist in the first place. The thoracoscopic lung-biopsy has become in our clinic a routine diagnostic procedure in almost all cases with diffuse alterations on the chest X-ray. It is also practised in some cases of pleural effusion of unclear genesis. The method competes with other procedures like needle biopsy, surgical biopsy, transbronchial biopsy and sometimes mediastinoscopy. Induction of an artificial pneumothorax is essential. The procedure is almost painless under local anaesthesia and very weel tolerated by the patient. No complications of any importance were observed. The results of 115 cases (over a period of 15 years) are presented and discussed. Because of the safety and the very high percentage of positive pathology (95%) we regard the method as a procedure of first choice.