The aim of this study was to determine how the guidelines published after this conference have spread. Pretherapeutic evaluation and treatment were assessed for all colon cancers diagnosed in a well-defined French population in 2000. Patients were classified either as managed according to the recommendations, or as undermanaged or overmanaged. Outside the emergency context, pretherapeutic work-up was classified as in conformity with the consensus in 48.0% of the cases, as undervalued in 21.9% and as overvalued in 30.1%. The resection rate at 90% was not far from the optimum. Pathological data allowed us to classify nearly all cases according to the tumour node metastasis classification; however, the number of examined nodes was below the recommendations in 30.8% of cases. Chemotherapy was performed according to the recommendations in 71.4% of cases, 23.1% were undertreated and 5.5% were overtreated. The multivariate analysis indicates that patients aged 75 years or more were less likely to receive chemotherapy than was recommended (P<0.001). This study suggested that the main reasons for not following guideline recommendations were inertia due to previous practices, difficulty to perform a recommended behaviour and lack of familiarity.