INTRODUCTION Fatty acids have an important role in structure and function of the nervous system. Recently, epidemiologic studies on neurodegenerative disorders have evaluated the usefulness of polyunsaturated fatty acids on multiple sclerosis. OBJECTIVE To examine recent studies, clinical trials, and reviews on the therapeutic effect of polyunsaturated fatty acids in multiple sclerosis. METHODS We conducted a search in MEDLINE/PubMed and Cochrane Library with the terms "fatty acids", "omega-3" and "omega-6" in combination with "multiple sclerosis". Articles were selected according to their relevance on the topic. RESULTS Epidemiologic studies have shown benefits of dietary supplementation with polyunsaturated fatty acids -especially omega-3- in relation to inflammatory, autoimmune and neurodegenerative disorders. In contrast, the studies do not show a beneficial effect of polyunsaturated fatty acids in multiple sclerosis. However, there are limitations related to design and sample issues in these studies CONCLUSIONS There is some evidence of a protective effect of polyunsaturated fatty acids on the risk of multiple sclerosis. Despite this, to date controlled trials have not produced definite results on the benefits of supplementation with polyunsaturated fatty acids in patients with multiple sclerosis. Any potential benefit will have to be confirmed in the long term.