OBJECTIVES: The potentially limited generalisability of RCT-based economic analysis may seriously restrict their relevance to policy-making. Therefore, the present study aimed to examine the costs of adjuvant treatment in stage III colon cancer based on real-world resource use. In addition, we determined the economic burden in the Netherlands. METHODS:   Real-world data were gathered from the Dutch population-based Cancer Registry supplemented with data from medical records in 19 hospitals. We were able to observe treatment patterns in clinical practice during 2005-2006 (N=427). From a representative patient sample (N=206), mean costs per patient were calculated in regard to the four most common treatment groups. Total costs for individual patients were determined by estimating resource use and unit costs of all relevant cost components. All costs were reported in euro 2007. RESULTS: Four percent of the patients received fluorouracil plus leucovorin (5FU/LV), 24% received capecitabine, 35% received 5FU/LV plus oxaliplatin and 37% received capecitabine plus oxaliplatin. Mean costs per patient amounted to €8,968, €9,901, €32,593 and €23,593 respectively. We found a substantial cost variation in the total costs obtained for individual patients as well as in each individual cost component. Inpatient hospital days, daycare treatments, outpatient visits and chemotherapy (leucovorin, capecitabine and oxaliplatin) were the most important cost drivers. Extrapolating the mean treatment cost per treatment group to all patients treated in 2005 and 2006 (n=2248) resulted in an economic burden of €26.1 million per year. CONCLUSIONS: Our results suggest a trend towards oxaliplatin plus either 5FU/LV or capecitabine as the preferred treatment for stage III colon cancer which is in line with national guidelines. Furthermore, a trend towards capecitabine is observed. This can be encouraged by lower treatment costs for capecitabine plus oxaliplatin over 5FU/LV plus oxaliplatin which may in part relieve the economic burden of stage III colon cancer in the future.