6153 Background: Failure mode and effects analysis (FMEA) is used in multiple industries to prospectively evaluate system safety and reliability. Using FMEA, we performed a systematic risk analysis in the radiation oncology (RO) setting. Methods: A visual map of the external beam RO process was created and divided into four sub-processes: consultation (C), simulation (SM), treatment planning (TP) and treatment delivery (TX). An 11-member cross-sectional, department committee reviewed the map to identify possible failure modes. Each mode was scored by 10 individuals and assigned a risk probability number (RPN) based on severity (S), frequency (F), and detectability (D). A 10-point scale, determined by consensus, was used to score each category. Modes within the S sub-process were re-scored by committee consensus. A higher RPN correlated with importance of a failure. A two-tailed t-test was used for significance. Results: The process map consisted of 269 different nodes and 131 failure modes were identified with RPNs from 8 to 240. The mean (± standard deviation) RPNs calculated for the C, SM, TP, and TX were 79.4 (± 33.2), 73.1 (± 26.1), 76.7 (± 24.1), and 87.2 (± 25.0), respectively. The mean RPN for TX was significantly greater (p < 0.003) than all other sub-processes. For TX, the mean S, F, and D scores were 6.6 (± 1.2), 3.3 (± 0.6), and 3.9 (± 0.7) compared to 4.9 (± 1.2) (p < 0.001), 3.9 (± 0.7) (p < 0.001), and 4.1 (± 1.5) (p < 0.05) for all other sub-processes. For the S sub-process, the group and individual mean scores were concordant for S and F of the failure and the total RPN. The individual mean D score, 4.1 (± 1.2) was significantly greater than the group, 3.6 (± 2.0) (p < 0.006). Conclusions: This first analysis using the validated FMEA tool systematically and quantitatively identified vulnerabilities in a complex, academic RO process before an error occurred. Relative RPNs can prioritize the risk of system failures and select interventions for safety improvement. Such an analysis could be used in other process-intensive oncologic areas. This serves as the basis for ongoing work in the appropriate application and limitations of FMEA for error reduction in medicine. No significant financial relationships to disclose.