Background: Definitive chemoradiotherapy (CRT) is recommended by the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Anal Carcinoma for all patients with stage I anal canal cancer. Because these patients were not well represented in clinical trials establishing CRT as standard therapy, it is unclear whether NCCN recommendations are being closely followed for stage I disease. This study identified factors that predict for NCCN Guideline-concordant versus NCCN Guideline-discordant care. Methods: Using the National Cancer Data Base, we identified patients diagnosed with anal canal carcinoma from 2004 to 2012 who received concurrent CRT (radiotherapy [RT] 45.0-59.4 Gy with multiagent chemotherapy), RT alone (45.0-59.4 Gy), or surgical procedure alone (local tumor destruction, tumor excision, or abdominoperineal resection). Demographic and clinicopathologic factors were analyzed using the chi-square test and logistic regression modeling. Results: A total of 1,082 patients with histologically confirmed stage I anal cancer were identified, among whom 665 (61.5%) received CRT, 52 (4.8%) received RT alone, and 365 (33.7%) received only a surgical procedure. Primary analyses were restricted to patients receiving CRT or excision alone, as these were most common. Multivariable analysis identified factors independently associated with reduced odds of CRT receipt: low versus intermediate/high tumor grade (adjusted odds ratio [AOR], 0.21; 95% CI, 0.14-0.29; P<.001), tumor size <1 cm vs 1 to 2 cm (AOR, 0.24; 95% CI, 0.17-0.35; P<.001), age ≥70 versus 50 to 69 years (AOR, 0.36; 95% CI, 0.24-0.54; P<.001), male sex (AOR, 0.63; 95% CI, 0.45-0.90; P=.009), and treatment at an academic versus a non-academic facility (AOR, 0.58; 95% CI, 0.41-0.81; P=.002). Conclusions: Despite the NCCN recommendation of CRT for stage I anal cancer, at least one-third of patients appear to be receiving guideline-discordant management. Excision alone is more common for patients who are elderly, are male, have small or low-grade tumors, or were evaluated at academic facilities.