60 patients had 1 to 7 biopsies during thoracoscopy under light anaesthesia without tracheal intubation. Biopsies were performed under direct vision using a separation puncture. Double-spoon biopsy forceps (5 mm in diameter) connected to a 120 watt diathermy apparatus avoided any air leak age and ensured haemostasis as the biopsy was taken. The dry weight of the biopsies ranged between 5 and 40 mg, allowing appropriate studies with light or electron microscope, for bacteriological and mineral analysis, and for hormone receptors search in cancer cases. A size 20 to 30 Charrière drain was left for a mean of 3 days. No serious complications arose. Ten patients had a 38 degrees C fever for a few hours. In one case early in the study a drain had to be changed on the third day. An histopathological diagnosis was made in 12 out of 14 patients with localised pulmonary opacities and in all 14 cases with diffuse opacities. In 32 cases of pleural involvement the presence or absence of concomitant lung involvement could be demonstrated. Asbestos fibres counts by electron microscopy correlated fairly with previous exposure to asbestos. The sensibility of the technique was 96% (percent of true positives) and the specificity 100% (percent of true negatives). Thoracoscopic lung biopsy may thus be compared very favourably to techniques of lung biopsy and deserves a larger studies in order to confirm its low morbidity.