Eicosapentaenoic acid is an ω-3 fatty acid abundantly available in marine organisms. (±)17(18)-DiHETE is one of the major metabolites produced when eicosapentaenoic acid (EPA) is incubated with various rat tissue homogenates or cynomolgus monkey seminal vesicles. The route of production of (±)17(18)-DiHETE likely proceeds through cytochrome P450-catalyzed epoxidation at the ω-3 double bond followed by conversion to the vicinal diols by epoxide hydrolase. EPA is also metabolized preferentially by Gaeumannomyces graminis to (±)17(18)-DiHETE.