Findings show brain serotonin (5-hydroxytryptamine (5-HT)) activity to be altered in individuals who have had bulimia nervosa (BN), even after substantial remission of symptoms. Such findings could reflect persistent sequelae due to BN, or a vulnerability 'trait' that exists independently of active eating-disorder manifestations. We compared women with full-blown BN (BN; n=22), BN in remission (BN-R; n=11), and no eating or psychiatric disturbances (n=22) on measures of platelet [(3)H]paroxetine binding, eating symptoms and psychopathology. The BN-R group showed normal-range scores on eating and psychopathological symptoms, but reductions in density (B(max)) of binding sites for paroxetine similar to those obtained in the actively ill women. Both BN groups had substantially lower B(max) than did healthy controls. Our results corroborate other findings indicating recovered BN patients to have anomalous 5-HT functioning. While such effects could represent a lasting 'injury' to the system, reported covariations between personality traits and 5-HT indices in BN encourage us to favor the argument that some alterations of 5-HT activity (in this case, consistent with reduced transporter activity) represent a 'trait' associated with the risk of developing BN and/or associated psychopathology.