Résumé : Stage III NSCLC represents a heterogeneous group and the ISS remains unsatisfactory in term of prognosis prediction. The aim of the present study was to determine the role of TTF-1 as prognostic factor in stage III NSCLC in addition to other known clinical factors. All stage III NSCLC patients treated in our hospital were retrieved and searched for biopsy specimens. TTF-1 was assessed by immunohistochemistry (Novocastra SPT24). Between 01/1987 and 07/2003, 108 assessable stage III NSCLC patients were included in the study. Their principal characteristics were: median age 64 years (range 37-83), male/female 81/27, squamous/non squamous 52/56, IIIA/IIIB 44/64, median Karnofsky PS 80 (range 20-100). Forty-four patients were positive for TTF-1 (squamous 25.0% versus non-squamous 55.4%). In multivariate analysis, only three factors were statistically significantly associated with better survival: good PS, surgery and creatinine level. CONCLUSION: In stage III NSCLC patients, good PS, resectability and low creatinine level but not TTF-1 are prognostic factors for survival.