The density of "peripheral-type" binding sites for benzodiazepines (PBS) in the rat pineal gland was reduced by approximately 50% three weeks after superior cervical ganglionectomy or exposure to constant light; the apparent affinity of [3H]Ro 5-4864 (the prototype ligand for these sites) remained unchanged. In contrast, neither the density of PBS nor the apparent affinity of [3H]Ro 5-4864 for these sites was altered in cerebral cortex by these procedures. The demonstration that PBS density is under neural control in the pineal gland suggests that these sites may have a physiologic role. The high density of PBS in pineal (approximately 24 pmol/mg protein) suggests that this tissue may be a useful model to study both the physiologic and pharmacologic function of these sites.