Background: Currently available data suggest that delaying the start of adjuvant chemotherapy in colon cancer patients has a detrimental effect on survival. We analysed which factors impact on the timing of adjuvant chemotherapy and evaluated the influence on overall survival (OS). Patients and methods: Stage III colon cancer patients who underwent resection and received adjuvant chemotherapy between 2008 and 2013 were selected from the Netherlands Cancer Registry. Timing of adjuvant chemotherapy was subdivided into: 64, 5-6, 7-8, 9-10, 11-12 and 13-16 weeks post-surgery. Multivariable regressions were performed to assess the influence of several factors on the probability of starting treatment within 8 weeks post-surgery and to evaluate the association of timing of adjuvant chemotherapy with 5-year OS. Results: 6620 patients received adjuvant chemotherapy, 14% commenced after 8 weeks. Factors associated with starting treatment after 8 weeks were older age (Odds ratio (OR) 65-74 versus <65 years 1.3 (95% confidence interval (CI): 1.14-1.58); OR >= 75 versus <65 years 1.6 (1.25-1.94)), emergency resection (OR 1.8 (1.41-2.32)), anastomotic leakage (OR 8.1 (6.14-10.62)), referral to another hospital for adjuvant chemotherapy (OR 1.9 (1.36-2.57)) and prolonged postoperative hospital admission (OR 4.7 (3.30-6.68)). Starting 5-8 weeks post-surgery showed no decrease in OS compared to initiation within 4 weeks (Hazard ratio (HR) 5-6 weeks 0.9 (0.79-1.11); HR 7-8 weeks 1.1 (0.91-1.30)). However, commencing beyond 8 weeks was associated with decreased OS compared to initiation within 8 weeks (HR 9-10 weeks 1.4 (1.21-1.68); HR 11-12 weeks 1.3 (1.06-1.59); HR 13-16 weeks 1.7 (1.23-2.23)). Conclusion: Our data support initiating adjuvant chemotherapy in stage III colon cancer patients within 8 weeks post-surgery. (C) 2015 Elsevier Ltd. All rights reserved.