Background: Adjuvant 5-fluoruracil-based chemotherapy significantly decreases mortality among patients with stage III colon cancer, but is less prescribed with rising age. We were interested in the pattern of adjuvant treatment and possible effects on survival among elderly patients. Patients and methods: All resected patients aged 65-79 with stage III colon carcinoma, diagnosed between 1995 and 2001 in the Comprehensive Cancer Centre South registry area in the Netherlands were included ( n =577). We examined determinants of receipt of adjuvant chemotherapy and their relation to survival. Results: The proportion of elderly patients receiving adjuvant chemotherapy increased from 19% in 1995 to 50% in 2001, but a large inter-hospital variation remained. In a multivariable analysis, females [odds ratio (OR) 0.5, P =0.006], patients with comorbidity [OR 0.5, P =0.005], and patients with a low socioeconomic status [OR 0.5, P =0.02] received less adjuvant therapy. Between 1995 and 2001 survival of elderly patients improved (hazard ratio 0.8, P =0.04). Conclusion: Although an increasing proportion of elderly patients with colon cancer are treated with adjuvant chemotherapy, many elderly patients still do not receive this treatment. As expected, receipt of adjuvant treatment decreased in the presence of comorbidity, but the clinical rationale for undertreatment of women and patients with low socioeconomic status is not clear.