The objective of this study was to explore the inter-relationship of three platelet measures of serotonergic function (5-HT): 5-HT Transporter Binding, 5-HT-2 Receptor Binding and 5-HT Content and to explore their inter-relationship with measures of aggression and impulsivity. 58 male subjects with personality disorder were studied. Numbers of platelet 5-HT Transporter and 5-HT-2 Receptor sites were assessed by examining the Bmax of 3H-Paroxetine Binding and the Bmax of 125I-LSD Binding to the blood platelet; 5-HT Content was assessed by measuring the amount of 5-HT in the platelet material. Life history of aggression was assessed by Life History of Aggression. Impulsivity was assessed by the Impulsivity Scale of the Eysenck Personality Questionnaire-II. Platelet 5-HT Transporter Binding correlated with both 5-HT-2 Receptor Binding and 5-HT Content; the latter two variables did not correlate with each other. Only Platelet 5-HT Transporter binding correlated significantly with LHA Aggression. These data suggest that while Platelet 5-HT Transporter binding correlates with both 5-HT-2 Receptor Binding and with 5-HT Content, that only 5-HT Transporter Binding represents a correlate of aggression in male personality disordered subjects.