122 patients, suspicious for silicoses, with a history of silicogen dust exposure, radiological changes and restricted lung function values were examined by mediastinal biopsy for securing the diagnosis. In 82 patients (67,2%) a silicosis could be confirmed by histological examinations of the mediastinal lymph nodes. A close association between silicosis in the lungs and in the lymph nodes is empirically suggested. If the histological findings were in compliance with suspicious radiological changes and patients history, silicosis was acknowledged as an occupational disease. In patients with beginning silicotic changes in the peripheral two upper lung fields associated with an hilar hyperplasia, a higher proportion of positive results could be found. The most positive alterations were found in the lymph nodes of the right hilus. The mediastinoscopical findings in other parts proved not to be so yielding. Therefore, in cases with anatomical difficulties the surgical examination should not be extended to other parts.