Diffuse interstitial lung disease due to a wide variety of conditions are amenable to diagnosis by means of clinical evaluation, bronchoalveolar lavage, transbronchial biopsy and lung biopsy. The recently introduced technique of thoracoscopic wedge biopsy provides the potential advantages of greater selection of biopsy site and reduced postoperative chest pain compared with the standard open lung biopsy Video assisted thoracoscopic lung biopsy was performed in twenty patients for diagnosis of diffuse in- terstitial lung disease during the period from January 1993 to June 1994. The ages of the patients ranged from 18 to 69 years(mean 48.5 years), and the patients consisted of 10 males and 10 females. In all twenty, thoracoscpic lung biopsy samples were obtained; 9 from left lower lobe, 7 from right lower lobe, 2 from right upper lobe, 1 from left upper lobe, and 1 from right middle lobe. All patients were correctly diagnosed. The two common diseases were usual in erstitial pneumonia(UIP)(8120) and mil- liary tuberculo si s(4120) . Mean duration of the chest drainage was 3.2 days. There was no complication.