Genetics has a entered golden post genomic era that promises to greatly improve our understanding of the etiology of complex familial disorders. Many forms of behavior are familial but Mendelian disorders are rare, and common conditions have complex inheritance. Twin and adoption studies confirm that major psychiatric disorders such as schizophrenia and bipolar affective disorder are highly heritable. There is also emerging evidence of some overlap between these disorders. Several susceptibility loci for schizophrenia have been identified, at least one of which is also a susceptibility gene for bipolar disorder. The first susceptibility genes involved in major psychiatric disorders have been identified and more will soon follow with the exploitation of emerging technologies that allow whole genome association studies. Pediatr Blood Cancer 2007;48:736–737. © 2007 Wiley-Liss, Inc.