Fifty six consecutive cases of mediastinoscopy are analysed. The procedure was performed without any complication and mortality. It is concluded that the mediastinoscopy is a safe procedure and causes little disturbance to the patient. The value of mediastinoscopy as a diagnostic procedure for mediastinal and pulmonary hilar masses is shown. In my series, mediastinoscopy was performed in 17 cases, which could not be diagnosed by other means, for purpose of diagnostic procedure. A histologic diagnosis was obtained in 11 of the 17 patients [64.7%]. The findings are 6 cases of tuberculosis, 2 cases of metastatic carcinoma, 1 case of primary carcinoma, and one case of noncaseating granuloma. The histologic diagnosis of carcinoma in patients believed to have non-resectable tumors could be obtained in 4 of the 7 cases [57.1%]. Three cases out of 32 patients with presumably resectable bronchial carcinoma were found to have mediastinal lymph node metastases. Two patients of 29 cases refused to be operated on. The remaining 27 cases had thoracotomy and resection was undertaken in all but 9 cases [33.3%]. [KTCS 1982;4:467-472]