Data from previous experiments in rats indicate that release of serotonin in the central nervous system increases renin and corticosterone secretion. To determine which serotonergic neurons are involved, lesions of the dorsal or median raphe nuclei were produced by local injections of 5,7-dihydroxytryptamine (5,7-DHT) in rats, and 2 weeks later, the renin responses to parachloroamphetamine (PCA) were determined. Plasma corticosterone was also measured. PCA produced significant increases in plasma renin activity and plasma corticosterone in sham-lesioned animals and animals with median raphe lesions. The plasma corticosterone response to PCA was also normal in rats with dorsal raphe lesions but the renin response was significantly reduced. The data support the hypothesis that serotonergic neurons in the dorsal raphe nucleus are part of a neural pathway mediating increased renin secretion, and that the stimulatory effect of serotonin on corticosterone secretion is mediated by a different pathway.