['This study aimed to analyze adjuvant therapy among patients with extrahepatic cholangiocarcinoma (EHC) at a national level.', 'The American College of Surgeons National Cancer Data Base was used to identify patients with resected EHC (pathologic stages 1-3) between 1998 and 2006 (n = 8741). Three groups were compared: surgery only (S, n = 5766), surgery plus adjuvant chemotherapy (AC, n = 450), and surgery plus adjuvant chemotherapy and radiation therapy (ACR, n = 1918). The study investigated how patient demographics, provider characteristics, and tumor-specific variables were associated with receipt of adjuvant therapy and overall survival.', 'Patients who received adjuvant treatment were more likely to be younger (median age S, 70 years; AC, 65 years; ACR, 63 years), in the highest income quartile (>$46,000: S, 38.3 %; AC, 43.4 %; ACR, 44.7 %), and treated at a community cancer center (S, 43.0 %; AC, 50.7 %; ACR, 52.9 %) (all p < 0.001). These patients also were more likely to have positive lymph nodes (S, 34.7 %; AC, 69.6 %; ACR, 63.3 %), positive surgical margins (S, 5.9 %; AC, 7.1 %; ACR, 10.7 %), and stage 3 disease (S, 21.4 %; AC, 37.8 %; ACR, 37.9 %) (all p < 0.001). Multivariate analysis of the entire cohort showed improved survival with ACR (hazard ratio [HR] 0.82; 95 % confidence interval [CI] 0.75-0.91). The survival benefit was independent of margin status (R0: HR 0.88; 95 % CI 0.79-0.97; R1: HR 0.49; 95 % CI 0.38-0.62).'] Is adjuvant Chemotherapy and Radiation Therapy Associated with Improved Survival for Patients with Extrahepatic Cholangiocarcinoma?