It has been clear for many years from genetic epidemiology that there is a substantial genetic component to schizophrenia. However, inheritance is complex and non-mendelian with liability to the disorder probably depending upon the combined effects of several, perhaps many, genes together with environmental factors. This genetic complexity together with the fact that the diagnosis of schizophrenia has no validating biology criteria has hampered attempts to identify specific risk genes. In recent years, replicated findings have begun to emerge from positional genetic and convergent genomic work implicating several specific genes; although in no case have nucleotide changes associated with direct risk or protective effects been unequivocally identified. Recent genetic findings are consistent with a primary deficit in synaptic function, but other explanations, such as defects in myelination, are equally plausible. Finally it is perhaps not surprising that some “schizophrenia genes” appear also to confer risk to schizoaffective disorder and bipolar disorder and show associations with clinical syndromes rather than specific categorically defined diagnoses.