This study compared serotonergic function, as assessed by prolactin response to fenfluramine, in males with compulsive personality disorder, males with noncompulsive personality disorders, and normal control subjects. The two patient groups did not differ in age, depression status, suicide history, or comorbid borderline personality disorder. However, compulsive personality disorder patients had significantly greater impulsive aggressive scores than the noncompulsive patients and significantly blunted prolactin responses compared with the non-compulsive patients and normal control subjects. In the combined patient group, total compulsive personality disorder traits correlated positively with impulsive aggression score and inversely with prolactin response. These results support the hypothesis that impulsive and compulsive symptoms do not simply lie at opposite ends of a phenomenological and neurobiological spectrum, but rather have a complex intersection and may both correlate with serotonergic dysfunction.Abstract Teaser