Objective: To review the literature regarding the use of fish oils in the treatment of psychiatric illness. Method: A Medline search was conducted in September 1999. Results: Five papers have investigated omega‐3 fatty acids levels in depression. One study used omega‐3 fatty acids as an adjunctive therapy in bipolar disorder. Four studies used fatty acids as an adjunctive therapy in schizophrenia. Conclusion: There is a great deal of current research in this field. While omega‐3 fatty acids levels may be lowered in depression, there are no data suggesting that omega‐3 fatty acids are effective. One paper indicates that omega‐3 fatty acids are effective in bipolar disorders. The data on schizophrenia are conflicting. Omega‐3 and omega‐6 fatty acids have proved effective. Most of the evidence suggests that the main effect is an improvement in negative symptoms. One recent study showed that omega‐3 fatty acids had no effect on negative symptoms.