917 patients with intrapulmonary lesions were studied by transthoracic needle biopsy. 460 cases in which both the puncture technique (general anaesthesia with artificial ventilation using a CARLENS' doublelumen catheter, puncture under X-ray amplifier-TV-guidance) and the control measures (fluoroscopy immediately performed after the puncture biopsy X-ray film 24 hours later) in accordance were analysed. The diagnostic yield was 72.5% in disseminated lung lesions using HAUSSER'S split needle. In localized coinlike lesions there was a positive diagnostic rate of 72.6%. The complication rate in these two groups was 63% and 54.8% respectively (p > 0.05). The authors use the transthoracic puncture biopsy in relation to the roentgenologic appearance and to the localization of the pathologic structures. They decline to perform the transthoracic puncture biopsy as a bed side method.