In the period 1988-1992, 74 consecutive radically resected patients with NSCLC were randomised to postoperative radiotherapy or surgery alone in order to evaluate the influence of postoperative radiotherapy on survival. There were 61 males and 13 females, aged 35-80 years, median 59 years. Their distribution by stage was as follows: pT1N2 = 19, pT2N2 = 54, pT3N2 = one patient; histology: 32 squamous, 32 adeno and 10 large cell carcinomas; surgery: atypical resection in six, lobectomy in 27, bilobectomy in ten, and pneumonectomy in 31 patients. In 27 patients, only one lymph node in a single mediastinal lymph node site was affected; in 31 patients more than one lymph node in one site; in 16 patients more sites were affected. In 35/74 patients radiotherapy of hilar and mediastinal sites with 3000 cGy in 2 weeks was performed. On December 31, 1994, 19 patients (26%) were still alive; 39/55 patients died of the following causes: locoregional failure-10(26%), distant metastases- 25 (64%), other tumor-unrelated causes-four patients (10%). Five-year survival rates did not show statistically significant differences between the irradiated and surgically treated patients only with respect to sex, pTNM stage, histology and frequency of locoregional failure. The number of metastatic mediastinal lymph nodes was the only significant prognostic factor (P < 0.005) in both randomised groups.