Based on randomized data, neoadjuvant chemoradiotherapy has been incorporated into the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for stage II-III rectal cancer. Factors associated with nonadherence to evidence-based guidelines for neoadjuvant radiotherapy (RT) were examined at dedicated cancer centers. The prospective NCCN Oncology Outcomes Database for Colorectal Cancers was queried for patients with stage II-III rectal cancer who underwent a transabdominal surgical resection between September 2005 and June 2012. Multivariable logistic regression was used to identify factors associated with omission of RT. Among 1199 identified patients, 1119 (93%) received neoadjuvant RT, 51 (4%) did not receive RT, and 29 (2%) received adjuvant RT. Among 51 patients not receiving RT, only 19 (37%) were referred and evaluated by a radiation oncologist. On multivariable analysis, clinical factors associated with not receiving RT included a history of prior pelvic RT (adjusted odds ratio [aOR], 23.9; P=.0003), ECOG performance status of 2 or greater (aOR, 11.1; P=.01), tumor distance from the anal verge greater than 10 cm (aOR, 5.4; P=.009), age at diagnosis of 75 years or older (aOR, 4.43; P=.002), body mass index of 25 to 30 kg/m2 and less than 25 kg/m2 (aOR, 5.22 and 4.23, respectively; P=.03), and clinical stage II (aOR, 2.27; P=.02). No significant change was seen in RT use according to diagnosis year, nor was any correlation seen with distance to the nearest RT facility. Concordance with NCCN Guidelines for neoadjuvant RT is high among NCCN Member Institutions. After adjusting for clinical characteristics that increase the risk for RT toxicity, including history of pelvic RT and high comorbidity burden/low functional status, the authors found that non-obese patients of advanced age or those with more favorable clinical features were more likely to not receive RT.