In unresectable non-small cell lung cancer (NSCLC) with a patent mainstem bronchus, some studies of obstructive tumors, showed (1) a poor role for irradiation in obtaining efficient debulking and (2) an interest in preliminary laser treatment in these patients. Cryotherapy is another method to obtain debulking. Moreover, several studies showed that cryotherapy would increase the radiosensitivity of a tumor. We performed a preliminary protocol combining successively initial cryotherapy followed by irradiation in inoperable NSCLC (either for local or functional contraindications). Thirty-eight patients were included and treated first by cryotherapy performed under general anesthesia and then with external irradiation in a curative intent. The efficiency of cryotherapy assessed on bronchoscopy was found to be volume-efficient (VE) in 26 of the 38 patients and non-volume-efficient (NVE) in the other 12 patients. After irradiation in the VE group, 17 of the 26 patients had no bronchial residual tumor (NRT). In contrast, all of the patients in the NVE group had a bronchial residual tumor (RT). Survival in the VE group (median, 397 days) was significantly higher than the survival of the NVE group (median, 144 days). Survival was found to be independent of the surgical contraindication (local or functional). The best survival was associated both with the efficiency of the initial debulking (VE) by cryotherapy and with the local control (NRT) induced by the irradiation (median, 560 days). Local control was obtained in 65 percent (17/26) of the cases in the VE group and was never observed in the NVE group. In our study the VE group's local control is better than the 35 percent usually reported after irradiation alone. These results argue for the efficient potentiation of irradiation by cryotherapy.