PURPOSE: We report the recruitment rate, reasons for and factors influencing non-participation, and descriptive results of a randomized controlled trial of two different exercise programs for patients with colon cancer undergoing adjuvant chemotherapy. METHODS: Participants were randomized to a low-intensity, home-based program (Onco-Move), a moderate- to high-intensity, combined supervised resistance and aerobic exercise program (OnTrack), or Usual Care. Non-participants provided reasons for non-participation and were asked to complete a questionnaire assessing behavioral and attitudinal variables. Trial participants completed performance-based and self-reported outcome measures prior to randomization, at the end of chemotherapy, and at the 6-month follow-up. RESULTS: Twenty-three of 63 referred patients agreed to participate in the trial. All 40 non-participants provided reasons for non-participation. Forty-five percent of the non-participants completed the questionnaire. Those who did not want to exercise had higher fatigue scores at baseline and a more negative attitude toward exercise. Compliance to both programs was high and no adverse events occurred. On average, the colon cancer participants were able to maintain or improve their physical fitness levels and maintain or decrease their fatigue levels during chemotherapy and follow-up. CONCLUSIONS: Recruitment of patients with colon cancer to a physical exercise trial during adjuvant chemotherapy proved to be difficult, underscoring the need to develop more effective strategies to increase participation rates. Both home-based and supervised programs are safe and feasible in patients with colon cancer undergoing chemotherapy. Effectiveness needs to be established in a larger trial. TRIAL REGISTRATION: Netherlands Trial Register - NTR2159.