Video-assisted thorocotomy (VATS) was performed to 10 patients to whom diagnosis couldn’t done with closed pleura biopsy betvveen June of 1995 and december of 1997 at the clinic of chest Surgery of Medical Faculty of Selçuk Üniversity. 5 of the cases were female and 5 of them were male. The smallest case was 28 years old, the eldest case was 80 years old and average age of ali cases was 55.7. VATS was performed to 5 of ali cases from the right, and to 5 of them from the left side. At the 9 cases biopsy was taken with VATS, İt 1 case biopsy vvasn't effective, for this reason öpen biopsy was one with thoractomy. Ali of the cases in whom biopsy were done with VATS absolute diagnosis have been done. İn the 4 of these cases diagnosis was malign mesotelioma, in 3 of them diagnosis was tubercülosis, in 2 of them diagnosis was nonspesific pleuritis. İn the thorocotomy performed patient the diagnosis was metastasis of adenocarcinoma. Complications and mortality vvasn't seen in any of the cases.