Administration of the anorectic agent, dexfenfluramine (DFEN) to rats induced dose- and time-dependent expression of Fos-like immunoreactivity in several discrete brain regions of rats. At moderate doses, the regions showing the most intense Fos immunostaining included the bed nucleus of the stria terminalis, the lateral part of the central amygdala, midline thalamic nuclei, habenular nuclei, lateral parabrachial nucleus, and nucleus of the solitary tract. It is suggested that these nuclei, many of which are known to receive gustatory or visceral input, may form part of a functional circuit via which DFEN modulates food intake. Rats that were made hungry by either food deprivation or administration of insulin also showed induction of Fos in several brain regions, but only that in the supramamillary/ventral tegmental area was suppressed by pretreatment with an anorectic dose of DFEN. The functional significance of these sites requires further investigation.