Aims: To describe variation in the utilisation rates of primary radiotherapy for patients with rectal cancer in the Netherlands, focusing on time trends and age effects. Materials and methods: Data on primary non-metastatic rectal cancer were derived from the population-based cancer registries of four comprehensive cancer centres (regions) in the Netherlands (1997–2008, n = 13,055). Results: An increase in the utilisation rate was noted for the four regions, from 37–46% in 1997 to 66–76% in 2008, for both genders. This increase was found predominately for preoperative radiotherapy (from 13–31% to 58–67%) and (unsurprisingly) was most pronounced for stage T2–3 patients (from 9–27% to 68–80%). The probability of receiving radiotherapy decreased with age: the odds of receiving preoperative radiotherapy was reduced in patients aged 65 years and older, as well as the odds of receiving postoperative radiotherapy in those aged 75 years and older, which remained significant after adjustment for stage, gender and region. Regional differences persisted in multivariable analyses, i.e. the odds of receiving preoperative radiotherapy was reduced in two regions: odds ratio: 0.4 (95% confidence interval: 0.4–0.5) and 0.7 (0.6–0.8). The odds of receiving postoperative radiotherapy was significantly increased in these regions [odds ratio: 2.6 (2.2–3.2) and 1.6 (1.3–1.9), respectively] and reduced in another [odds ratio 0.8 (0.6–0.96)]. Conclusions: The utilisation rate of radiotherapy for rectal cancer increased significantly over time, particularly for preoperative radiotherapy and was most pronounced for T2–3 patients. Due to national multidisciplinary treatment guidelines, regional differences became limited in recent years after adjustment for age and stage of the disease. A low utilisation rate of radiotherapy was seen in women and elderly patients.