Plasma dopamine, β-carbolines (norharman, harman) and isoquinolines ((R)- and (S)-salsolinol) were examined for their relationship to antisocial tendencies in 138 drinking men with an alcohol dependence syndrome according to ICD-10 criteria. Antisociality was assessed according to the following criteria: delinquency, involvement in fist-fights and homelessness. The personality structure was documented by the Tridimensional Personality Questionnaire of Cloninger. An early age of onset of alcohol dependence and a high degree of 'novelty seeking' were associated with antisocial tendencies. Of the β-carbolines and isoquinolines, harman and (S)-salsolinol were significantly decreased among antisocial alcoholics. Norharman, (R)-salsolinol and dopamine were not associated with antisocial personality. The contribution of endogenous alkaloids to the biological characterization of antisocial tendencies in alcoholics is described.