Colorectal cancer occurs mainly in elderly patients. Recent estimation showed that in France more than 50% of the patients diagnosed with a colorectal cancer are 70 years old or more. Adjuvant chemotherapy has demonstrated a benefit on disease-free survival and overall survival after a stage III colon cancer resection. Nevertheless adjuvant chemotherapy is poorly used in elderly patients. Prognostic improvement with chemotherapy based on 5FU is suggested by a post-hoc analysis of randomized prospective clinical trial. But elderly patients in this study were highly selected and patients older than 80 represented only 0.7% of the total population. Thus, there is still a concern about the benefit of adjuvant 5FU-based chemotherapy in very elderly unselected patients. The recommended treatment for stage III adjuvant chemotherapy is a combination of fuoropyrimidine and oxaliplatin. Nevertheless oxaliplatin did not demonstrated survival advantage in elderly patients. Altogether there are still two matters of debate: * First, is there a benefit of fluoropyrimidine-based adjuvant chemotherapy for unfit elderly patients? * Second, is there a benefit of oxaliplatin-based adjuvant chemotherapy for fit elderly patients? The aim of this randomized phase III study is to evaluate the benefit for disease-free survival of adjuvant chemotherapy in elderly patient and which chemotherapy. The elderly patient population will be dichotomized into two groups according to physician's choice after a multidisciplinary evaluation involving a geriatrician, with two different randomization assignments. The patients with an expected life-expectancy below 4 years according Lee score are excluded of this study. Some biological tumour abnormalities are more frequently observed in elderly (i.e. mismatch repair deficiency), therefore an evaluation of specific biological prognostic factors is needed in elderly population.