Recent research has shown that depression and a range of physical illnesses, including heart disease, metabolic syndrome, and type 2 diabetes, have an inflammatory etiology. The long-chain omega-3 fatty acids (omega-3s) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in fish and fish-oil products, may protect against these illnesses, in part because they lower inflammation. This article reviews the recent research on omega-3s and women's mental health, with a particular focus on the perinatal period. These studies include population studies examining fish consumption and studies testing the efficacy of EPA and DHA as treatments for depression. Although the findings are mixed, the majority of studies indicate that EPA has efficacy in treating depression either alone or in combination with DHA and/or antidepressant medications. The role of DHA alone in mental health is less clear, but it is generally combined with EPA and appears to have a beneficial effect. In moderate doses, EPA and DHA appear safe for pregnant and postpartum women, and they are well tolerated by patients.