Pleural brushing can be performed under thoracoscopic examination. The combined use of all three methods of diagnosis (macroscopy, biopsy, cytology) achieved optimal diagnostic results. From September 1980 to October 1981 we have performed 150 thoracoscopies for pleural effusions, while the results of conventional pleural cytology and biopsy were negative. In 108 cases pleural brushing and biopsy were both performed. The diagnosis was in 37 cases non malignant disease states associated with effusions and in 71 cases tumoural effusions. Among the 37 cases of non malignant diseases states associated with effusions were 6 mechanical effusions, 27 inflammatory processes, 4 infectious processes. Among the 71 cases of tumoural effusions were 3 benign pleural lipomas, 50 metastatic carcinomas, 18 carcinomatous mesotheliomas. We studied the diagnostic accuracy of pleural brushing: in non malignant diseases pleural brushing show the non tumoural features of the process, in metastatic tumours biopsy was positive in 80% of the cases; pleural brushing in 78% of cases; taken together they allowed the diagnosis in 86% of the cases, in carcinomatous mesotheliomas biopsy was positive in 82.3%, pleural brushing in 78%; taken together they allowed the diagnosis in 89% of the cases. Pleural brushing allows a rapid cytological diagnosis, enhances the histological results and may be used to get cellular material in areas dangerous to biopsy.