The family of resolvins consists of omega-3 fatty acid-derived mediators, including E series resolvins generated from eicosapentaenoic acid (EPA), and carry potent anti-inflammatory properties. Here, we report the isolation, identification, and bioactions of resolvin E2 (RvE2), which is 5S,18-dihydroxy-eicosapentaenoic acid. RvE2 stopped zymosan-induced polymorphonuclear (PMN) leukocyte infiltration and displayed potent anti-inflammatory properties in murine peritonitis. We also demonstrate that human recombinant 5-lipoxygenase generates RvE2 from a common precursor of E series resolvins, namely, 18-hydroxyeicosapentaenoate (18-HEPE). Furthermore, the initial 5-hydroperoxide intermediate was also converted to a 5(6)-epoxide intermediate in RvE1 formation. These results demonstrate that RvE2, together with RvE1, may contribute to the beneficial actions of omega-3 fatty acids in human diseases. Moreover, they indicate that the 5-lipoxygenase in human leukocytes is a pivotal enzyme that can produce both pro- and anti-inflammatory chemical mediators.