Schizophrenia is a heritable disorder. The genetic architecture of schizophrenia is complex and heterogeneous. This article discusses genetic studies of childhood-onset schizophrenia (COS) and compares findings in familial aggregation, common allele, and rare allele studies of COS with those for adult-onset schizophrenia (AOS). COS seems to be a rare variant of AOS with greater familial aggregation of schizophrenia spectrum disorders and higher occurrence of rare allelic variants. The usefulness of genetic screening for diagnosis and individualized treatment is limited; however, identifying common pathways through which multiple genes adversely affect neural systems offers great promise toward developing novel pharmacologic interventions.