Studies of bulimia nervosa (BN) often report decreased brain serotonin (5-hydroxytryptamine: 5-HT) activity. Across populations, impulsivity has been linked to reduced 5-HT activity, but compulsivity has been associated (at least inconsistently) with an increase. We therefore became interested in the association between behavioral-trait variations and 5-HT status in BN. In 56 bulimic and 29 non-bulimic women, we measured eating symptoms, personality traits, platelet paroxetine binding, and neuroendocrine responses following oral meta-chlorophenylpiperazine (m-CPP). Relative to normal eaters, bulimic women showed reduced density (Bmax) of platelet paroxetine-binding sites, blunted prolactin (PRL) responses following m-CPP, and (as a trend) lower basal PRL levels. However, after effects of binge-purge frequencies, body mass, and other extraneous factors were controlled, PRL levels at baseline and other moments in the serial sampling varied systematically with presence of impulsive and compulsive traits. PRL was generally low in BN, but 'high-compulsive'/'low-impulsive' traits were associated with higher (normal-range) PRL values. Comparable trait-related variations were not observed on paroxetine-binding indices. Our findings suggest that 5-HT status in BN may correspond to impulsive or compulsive traits, and they encourage multidimensional modeling of the pathophysiological role of 5-HT in BN.