Bombesin (BBS) administered into the lateral cerebral ventricles suppresses food intake. Suppression of food intake, however, is accompanied by arousal of competing behaviors such as grooming and increased locomotion, which are atypical of normal satiety. We have found that BBS infused into the fourth cerebral ventricle in rats reduces food intake at doses one-tenth to one-hundredth of those required via the lateral ventricle. In addition, the lowest fourth ventricular dose that significantly reduced food intake did not increase locomotor activity. These data suggest that the hindbrain may be a more sensitive site for BBS-induced suppression of feeding than forebrain sites and that feeding and locomotor effects of BBS may involve dissociable neural substrates.