Computed tomography (CT) is the non-invasive staging procedure of choice for assessment of metastasis to mediastinal lymph nodes in patients with bronchial carcinoma. Cervical mediastinoscopy can provide histologic evidence of mediastinal spread to the peritracheal, tracheobronchial and subcarinal lymph nodes. Sub-aortic and para-aortic nodes cannot be sampled via this route. The present study was performed to assess the staging value of the parasternal mediastinoscopy as a separate entity. Cervical and parasternal mediastinoscopy was performed in 37 patients with a proven diagnosis of non-small cell carcinoma of the left upper lobe. In 16 patients lymph node or tumor tissue could be biopsied via the parasternal route, in 21 patients no parasternal biopsy was taken. Of the 16 cases with biopsies, only one was positive (6%). Histologic examination of lymph node biopsy tissue was false negative in one other patient (6%). Of the 21 patients without biopsies taken during parasternal mediastinoscopy, three (14%) had proven lymphogenic spread to the subaortic and para-aortic nodes, detected at thoracotomy. The parasternal procedure changed treatment in only one patient (3%). Diagnostic sensitivity was 20%. It is concluded that parasternal mediastinoscopy should not be used as a routine staging procedure in patients with left upper lobe lung cancer.