At the NIAAA intramural research program, in collaboration with investigators at the Department of Psychiatry, University of Helsinki, we have mounted an extensive research program on early onset male alcoholism. A central serotonergic deficit is common among these patients. This finding has led to behavioral, biochemical, physiological and molecular genetic studies on the serotonin system in early onset, antisocial and violent male alcoholics and in appropriate control populations. The results of the studies completed by the fall of 1993 are summarized in this communication.