OBJECTIVE To review the data that support the role of genetic factors in the predisposition to suicidal behavior and to examine whether or not these factors are part of the genetic liability to mood disorders. To review molecular genetic studies carried out in suicidal behavior. METHODS A review of the literature was carried out by means of systematic bibliographic database searches and complemented by searches in the references of relevant publications. RESULTS There is consistent evidence suggesting that genetic factors play an important role in the predisposition to suicide and suicidal behaviors. Although there is important overlap between suicide and mood disorders, a common genetic liability seems unlikely. It is possible that part of the predisposition to suicide may be transmitted via the presence of impulsive and impulsive-aggressive behaviors. An increasing number of molecular genetic studies have been carried out in subjects with suicidal behavior. There is some support for a role of some genes that code for components of the serotonergic pathway in the etiology of suicidal behavior, but these studies are still preliminary. CONCLUSIONS Further studies are needed at the epidemiological, clinical and molecular level to better characterize the genetics of suicide. These should control for the presence of behaviors that are considered as part of the phenotypic spectrum of suicide.