Between June 1973 and February 1979, 409 patients with inoperable advanced non-oat cell carcinoma of the lung were randomized on RTOG protocol 73-02. Three treatment arms were evaluated: 40 Gy split course, 30 Gy continuous course, and 40 Gy continuous course. Patients were also randomized to receive cytoxan or no further therapy following irradiation. Three hundred sixteen patients were evaluable. Palliation of symptoms was achieved in 60% with 1/4 of the patients becoming symptom-free. Complete regression of local and regional tumor was produced in 15% and partial regression in 26%. There is no significant difference between the treatment arms in these objective response rates. Median survival times were approximately 6 months. No significant benefit was demonstrated by the adjuvant use of Cytoxan. Although the number of complete responses produced was relatively small, patients achieving a complete response had a significantly longer median survival than the remaining patients, i.e., 14.5 months versus 6 months. Significant toxicity occurred in fewer than 6% of patients. Radiation pneumonitis counted for the majority of these adverse reactions. Toxicity occurred somewhat more often in the group treated with 40 Gy split course therapy. Implications for further studies are discussed.