Background: Mental illness is now being recognized as a major public health problemrnthroughout the world. Schizophrenia and bipolar disorder are chronic diseases of the centralrnnervous system that usually begin in young adulthood and have various degrees of severity.rnWhile many microbial agents have been proposed as risk factors for schizophrenia, manyrnrecent studies have focused on members of the viral family Herpesviridae as well as thernprotozoan organism Toxoplasma gondii.rnOBJECTIVES AND METHODS: The present study was conducted to detect the presencernof IgG antibodies against Herpes Simplex Viruses type 1 and 2 using ELISA methods in orderrnto know the association between Herpes Simplex Viruses type 1 and 2 infection and psychoticrnepisodes. A case control study was conducted from March 2009 to May 2009 on 216 casesrnof schizophrenia, 199 bipolar disorder patients, 80 healthy controls and about 349 otherrnclose relatives.rnRESULTS: Among study subjects HSV-1 seroprevalence was 97.9% and HSV-2rnseroprevalence was 13.3%. HSV-1 seroprevalence was 98.6% in schizophrenics, 96% inrnbipolar disorder cases and 98.4% in controls (both relative and non relative control). HSV-2rnseroprevalence was 7.9% in schizophrenics and 15.4% in bipolar disorder cases and 15.2%rnin controls (both relatives and non relatives). There was no significant difference in thernprevalence of HSV-1 across different age groups and between males and females. HSV-2rnprevalence was higher in females than males. As age advanced HSV-2 prevalence wasrnincreased. There was no association between HSV-1 infection and either schizophrenia orrnbipolar disorders. HSV-2 seroprevalence was significantly lower in schizophrenia casesrncompared to their relative controls.rnCONCLUSION: As age advanced HSV-2 prevalence increased. HSV-2 prevalence wasrnhigher in females than males. HSV-2 seroprevalence was significantly lower inrnschizophrenia cases compared to their relative controls. Future studies should focus onrnnewly diagnosed schizophrenics or bipolar disorder cases.