Background and purpose:Despite evidence for the efficacy of radiotherapy in stages II and III rectal cancer, utilization rates remain low. The aim of this study is to examine patient, provider and service factors affecting utilization of radiotherapy in rectal cancer patients. Materials and methods: Patients with a diagnosis of curable rectal cancer were identified from the colorectal tumor databases of three Sydney Area Health Services between 1994 and 2001. Data were collected on tumor characteristics such as site and stage, provider factors such as type of surgery and surgeon caseload, and patient factors including socioeconomic status and access to radiotherapy. Results: Thirty-five percent of stage II and 57% of stage III rectal cancer patients received radiotherapy. Independent determinants of utilization were age less than 70 years (odds ratio, 2.96; 95% confidence interval, 1.75-5.03), high-volume surgeons (OR, 1.95; 95% CI, 1.17-3.24), stage III disease (OR, 2.06; 95% CI, 1.25-3.41) and abdominoperineal resections (OR, 3.67; 95% CI, 1.94-6.94). Conclusion: Radiotherapy utilization rates remain low. Age, and being referred to a surgeon with a high caseload, has a greater impact on radiotherapy utilization than other provider, socioeconomic or service factors.