Background: Serotonergic system abnormalities have been implicated in the pathogenesis of schizophrenia. The 5-HT2A receptor gene polymorphism has long been implicated to play a role in the pathogenesis of schizophrenia. Aim: In this study, we assessed the relationship of schizophrenia and its subgroups with 5-HT2A receptor gene polymorphism, and attempted to evaluate a possible correlation between the severity and prognosis of the illness and 5-HT2A receptor gene polymorphism. Method: Our study comprised 141 unrelated subjects who strictly met DSM-IV criteria for schizophrenia, and 79 healthy unrelated controls, all of Turkish origin. A clinical evaluation of all patients was accomplished applying the Brief Psychiatric Rating Scale (BPRS) test. The analysis of 5-HT2A receptor gene polymor...