The behavioral and physiological effects of electrical stimulation of the nucleus locus coeruleus (LC) were studied in the awake rat. LC electrodes consistently supported high rates of self-stimulation (SS). LC stimulation also inhibited spontaneous cellular discharges in the hippocampus (HPC). Both the LC-induced inhibition of HPC units and the LC-evoked SS behavior were antagonized by alpha-methyltyrosine and 6-hydroxydopamine. In addition, chlorpromazine and diethyldithiocarbamate antagonized LC-induced inhibition of HPC units. D-Amphetamine facilitated SS behavior and reduced spontaneous HPC unit activity. The reinforcing properties of LC stimulation correlate closely with inhibition of cellular activity in the hippocampus; both actions appear to be mediated by norepinephrine.