Schizophrenia, which is also called "split personality," is a complex and multifactorial mental disorder with variable clinical manifestations. It perhaps represents several diseases and occurs throughout the world. It is a more-prevalent disorder among homeless people and is clinically characterized by hallucinations and delusions. The pathophysiology of schizophrenia is not localized to a single region of the brain and the etiology of this illness is not understood. Because of its complex pattern of inheritance, genetic techniques are not readily applicable in identifying the genes responsible for this disorder. Family, twin, and adoption studies, however, provide strong but indirect support for genetic components in the etiology of schizophrenia. Extensive linkage analyses now suggest that susceptibility genes may be present on chromosomes 5q, 6p, 8p, 13q, 18p, and 22q. Identification and characterization of these and other genes, as well as non-genetic factors, is one of the greatest challenges in biomedicine. This may ultimately lead to the development of a new line of effective and safe drugs or treatments for its prevention or cure.