Background: Racial differences in prostate cancer (PCa) outcomes are widely observed, irrespective of risk stratum at diagnosis. The primary study aim was to compare distant metastasis-free survival (DMFS) for African American (AA) and Caucasian American (CA) military health care beneficiaries undergoing radiation therapy (RT) for PCa over 20+ years. Methods: A retrospective cohort study of Center for Prostate Disease Research Multi-Center National Database enrollees was conducted. Eligibility requirements included a diagnosis with biopsy-confirmed PCa between January 1, 1989 and December 31, 2013, primary treatment ( < 6 months post-diagnosis) with external beam radiation therapy (EBRT) or brachytherapy (BRY), and ≥2 years follow-up. EBRT combined CT-based, 3D conformal, and intensity modulated RT (IMRT). DMFS was compared across race using Kaplan Meier (KM) estimation curve analysis, stratified by treatment type (EBRT vs. BRY). Multivariable (MV) Cox Proportional Hazards (PH) analysis was used to model DMFS as a function of race, stratified by treatment type (EBRT vs. BRY), controlling for clinical covariates. Results: Of the 4,299 eligible men who had primary RT, 2,022 (77.6%) had EBRT and 583 (22.4%) had BRY (N = 2605). Among EBRT patients, 28% were AA and 66% were CA. For BRY patients, 18% were AA and 77% were CA. Median follow up times and ages were 6.7 and 69.8 years for EBRT patients and 6.9 and 65.4 years for BRY, respectively. In KM analysis race did not predict DMFS for EBRT group (p = 0.56) but there were significant racial differences among BRY group (p = 0.013). Table 1 shows DMFS estimates by race and treatment group. In MV Cox PH models, race did not predict DMFS among EBRT patients (p = 0.695); however, among BRY group, AA men had a 4.7-fold increased probability of developing distant metastasis compared to CA men (p = 0.045), controlling for age at RT, year of treatment, and NCCN risk stratum. Conclusions: In this racially diverse, equal access health care system, comparable DMFS was observed across patient race over this 20+ years for EBRT but not BRY patients who had significantly poorer DMFS. Subsequent work will examine cancer-specific survival, comorbidity, and prostate volume.