Through the secretion of corticosterone, the hypothalamo-pituitary-adrenal (HPA) axis is thought to play an important role in the regulation of caloric intake and dietary fat preference. In an earlier study, we demonstrated a positive correlation between urinary corticosterone output and dietary fat preference. Furthermore, dietary fat preference was augmented following chronic but not acute hypercorticosteronemia produced by exogenous corticosterone administration. These observations led us to explore whether the HPA axis of rats exhibiting high preference for fat may have exaggerated sensitivity to corticotropin-releasing hormone (CRH). The results of these studies show a delayed and blunted but more prolonged corticosterone response to CRH in the fat-preferring rats compared with that of the carbohydrate-preferring rats.