In this prospective study of 148 surgically treated patients with non-small cell carcinoma of the lung (NSCLC) who were followed for 5 to 7 years, we analyzed the prognostic value of mediastinal lymph node invasion (N2) and survival after 5 years depending on different characteristics. Forty-two (28.4%) patients were N2. Survival in this sample was 9%. Twenty-seven T2N2 patients (among whom survival was 13%) were selected from this group and classified according to whether lymph node invasion was intranodal (survival 39%) or extracapsular (survival 5%) (p < or = 0.05). We also evaluated the prognostic value of different ganglionic areas in accordance to the maps suggested by the American Thoracic Society (ATS). There were no survivors for areas 2, 8 and 9, and no patient with invasion of more than two areas lived more than 18 months. Significant differences in survival were found among patients with invasion of areas 10 and 11. We conclude a) that global analysis of N2 is of such little value in predicting survival that surgery is not justified unless screening criteria are applied; b) that extracapsular invasion rules out surgical treatment; c) that the prognostic value of ganglionic areas is not entirely clear, although the prognosis seems to be poorer for invasion of areas 2, 8 and 9 or invasion of more than 2 areas, and d) that invasion of area 10 would appear to be better classified as N2 than as N1.