This is a summary of a systematic review that evaluated the recent evidence regarding the effects of omega-3 fatty acids (FAs), primarily from marine oil supplements, on clinical and selected intermediate cardiovascular (CV) outcomes (i.e., blood pressure, lipid concentrations) and the association of omega-3 FA dietary intake and biomarkers with CV outcomes. The systematic review included 147 articles published between 2000 and June 2015. Studies that analyzed levels of fish (or other food) consumption without exact quantification of omega-3 FA intake were excluded from this review. The full report, listing all studies, is available at www.effectivehealthcare.ahrq.gov/omega-3/. This summary is provided to assist in informed clinical decisionmaking. However, reviews of evidence should not be construed to represent clinical recommendations or guidelines.