Family, twin, and adoption studies have firmly established the genetic basis for a majority of cases of schizophrenia. Several other psychiatric disorders probably represent alternative manifestations of this genetic liability. The underlying genetic mechanisms are not yet well understood, but the development of schizophrenia appears to involve a system of genes that interact with pre- and postnatal stressors. Recent reports of genetic linkage in schizophrenia have not been replicated, but the potential of molecular genetic technology makes us optimistic that the bases of this complex disorder will be uncovered in the near future.