Diploma Thesis Tiltle: „Polyunsaturated fatty acid supplementation for schizophrenia (Review)“ Objectives: The aim of the research is to determine whether supplementation with omega-3 and omega-6 polyunsaturated fatty acids to help people who suffer from schizophrenia, in order to reduce positive and negative symptoms of the disease. Materials and methods: On the Cochrane Library systematic review found Polyunsaturated fatty acid supplementation for schizophrenia (Review), followed by a further search of randomized controlled trials and systematic reviews that matched the inclusion criteria Cochrane systematic review. Last update of the search to date was 11.02.2009. A search was carried out by CINAHL, EMBASE, MEDLINE and PsycINFO. Search continued through the database MEDLINE, CENTRAL and DARE, using the key words schizophrenia and omega-3 fatty acids. After the literature search was made, R-AMSTAR assessment Cochrane systematic review and a new found systematic review. Results: 9 research has met the inclusion criteria. Five of them have compared the effect of ethyl-eicosapentaenoic acid (EPA-E) in comparison to placebo, of which one study examined the three different doses of EPA-E. Two studies have compared the eicosapentaenoic acid (EPA) with placebo. One study compared the difference between the effects of EPA and docosahexaenoic acid (DHA), as compared to placebo, while one compared gamma-linolenic acid (GLA) and placebo. What is the general situation is concerned, all the studies have shown that there is a clear need for neuroleptics. When comparing EPA and E-EPA to placebo, which is the mental state is concerned, in some studies PANNS results were improved and in some there was no difference between groups. There was no difference in patients who had previously left the study. In a comparison between the efficacy of EPA and DHA, as compared to placebo, the results favor the effect of eicosapentaenoic acid, however the difference was not significant. In addition, the study was conducted on a small sample size and short lasting. When comparing different doses of EPA, with respect to placebo, at doses of less than 1 g per day did not differ in groups, while the PANNS results were significantly improved in the group who took 3g per day. Adverse events occurred in one study. Conclusion: Based on the reviewed systematic reviews and randomized controlled trials does not support the replacement of eicosapentaenoic acid or its ester, ethyl-eicosapentaenoic acid, with antipsychotics. Also, there is no clear evidence that their supplementation reduce positive and negative symptoms of the disease.