Suicide attempts are one of the risk factors of suicide. Possible mechanisms by which Toxoplasma gondii may affect human behavior and it may also cause humans to attempt suicide. The aim of this study is to find out whether or not T. gondii is one of the reasons in suicide attempts. We investigated the seropositivity level for anti-Toxoplasma IgG and IgM antibodies by enzyme-linked immunosorbent assay in subjects who have attempted to suicide to find out whether there is a probable relationship between T. gondii and suicide attempts. In our study, we selected 200 cases of suicide attempts and 200 healthy volunteers. The sero-positivity level for anti-Toxoplasma IgG antibodies among suicide attempts (41%) was significantly higher than the control group (28%). This signifies that there might be a causal relationship between toxoplasmosis and the etiology of suicide attempt. (c) 2010 Elsevier Ireland Ltd. All rights reserved.