RATS fed on a restricted feeding (RF) schedule of 4 h day−1 to produce a 15–20% reduction in body weight were killed before (starved) and after (fed) the presentation of food on the sixth day to compare 5-hydroxytryptamine (5-HT; serotonin) metabolism and synthesis rate in the hypothalamus with freely feeding (FF) controls. The RF rats showed lower 5-HT concentration and synthesis rate than FF controls. Restricted feeding did not decrease tryptophan concentration in the hypothalamus. However, RF-fed rats had lower tryptophan concentration than RF starved rats. 5-HIAA concentration was comparable in RF fed rats and FF controls but higher in RF starved rats. Possible implications of the findings in the pathogenesis of the food deprivation/starvation-related disease anorexia nervosa are discussed.