Most of the evidence from pharmacological studies supports the hypothesis of a serotonergic (5-HT) dysregulation in eating disorders (ED), though a specific alteration related to the major ED subtypes, anorexia (AN) and bulimia nervosa (BN), has not been identified yet, possibly because of changes over time in ED nosology. The aim of the present study was to verify whether differences in serotonergic activity, measured by platelet [3H]paroxetine binding, would validate current ED classification. Platelet [3H]paroxetine binding was investigated in 26 patients with eating disorders diagnosed in accord with DSM-IV criteria (AN, n=11; BN, n=15) and 26 normal weight controls of comparable age; ED symptomatology was assessed by the Diagnostic Schedule for Eating Disorders. ED patients had significantly lower B(max) values than controls (288.5+/-109.2 vs. 1396.8+/-251.3 fmol/mg), whereas the K(d) was not significantly altered (0.12+/-0.13 and 0.12+/-0.05 nM, respectively). Among patients, differences in B(max) were related neither to DSM-IV subtypes nor to clinical variables such as presence of binge-eating, purging, impulsive behaviors, or symptoms of depression. Although ED patients share a dysregulation in serotonergic activity, DSM-IV subtype classification was not validated by [3H]paroxetine binding, and hence does not correspond to a specific 5-HT profile.