RTOG Protocol 81-08, a feasibility study of hyperfractionated radiation therapy (HFX) with 1.2 Gy twice daily separated by 4-6 hours for non-small-cell cancer of the lung (NSCCL), was completed in 1983. Encouraging short-term results in a recently closed trial of HFX for NSCCL (RTOG 83-11) led to assessment of long-term outcome in the earlier trial. Of 120 evaluable patients who were assigned to total doses from 50.4 Gy to 74.4 Gy, all 5 of the 5-year survivors came from the 79 patients assigned to receive 69.6 Gy. The 5-year survival rates for the 79 patients were 14.3 +/- 9.4% for clinical RTOG Stage II, 5.9 +/- 4.0% for Stage III, and 3.2 +/- 3.2% for Stage IV. Combined Stage II and III 5-year survival rates were 8.3 +/- 4.0% for HFX 69.6 Gy compared to 5.6 +/- 1.5% for standard once-a-day irradiation in concurrent RTOG trials.