Genetic etiology in schizophrenia is widely accepted. However, many chromosomal sites were shown to characterize the families of patients with schizophrenia. This is probably due to the high genetic heterogenity of this illness. Thus, it is important to investigate the genetic factor in relatively genetically homogenous populations. Many studies have indicate that Ashkenazy Jews show relative gentic homogenity. Indeed, the genes responsible for most Mendelian disorders of Jewish peoples have been identified. The study will apply genome-wide mutation screening methods to identify candidate allells in subjects of Ashkenazi Jewish ancestry with multiplex schizophrenia.