One hundred and fifty-three patients with inoperable non-small cell lung cancer (NSCLC) treated with radiotherapy alone have been retrospectively analysed. Normalized Total Dose (NTD) as defined by Macejewski, TN-stage (AJC-system) and histology have been examined with respect to 5-year disease-free survival (DFS) and the patterns of failure so as to identify subgroups of patients that routinely should be treated with radical intent. The 5-year DFS for T1, 2-N0, 1 and T3-N0, 1 staged patients was 30% (7/23) and 25% (4/16) respectively when the tumor NTD (a/b = 10 Gy) was 56-64 Gy vs. 12% (5/41) and 0% (0/10) when the NTD was 48-55 Gy. This difference was statistically significant for the squamous cell histology group. The higher doses significantly altered the patterns of death in N0, 1 staged squamous cell carcinoma and adenocarcinoma patients. Forty-five percent (22/55) and 41% (12/29) of squamous cell and adenocarcinoma patients respectively, died from local relapse without evidence of distant metastases when NTD less tha 55 Gy were given vs. 21% (9/42) and 13% (2/15) when the NTD delivered was 56-64 Gy (p < 0.05). Although for N2, 3 staged patients or patients with direct extension of the tumor into the mediastinum death from local relapse occurred in 38% (10/26) of the high NTD treated patients vs. 51% (19/37) of the low-dose treated ones, the difference was not statistically significant. It is concluded that NSCLC patients should not à priori be considered as non-radiocurable. At least 30% of the patients with early local stages can be long-term disease-free survivors with radiation NTD up to 60 Gy and better results are to be expected with higher doses. Advanced T-stage without mediastinal involvement should be treated with radical intent since a high NTD could give cure rates of over 25%. The disappointing results for patients with mediastinal disease could perhaps be attributed to the low NTD delivered. For patients with good performance status, hyperfractionated regimens delivering high tumor doses should be tested and chemotherapy should be adapted to these radiation treatment schedules.