The renorenal reflex responses to renal mechano-(MR) and chemoreceptor (CR) stimulation have been examined in anesthetized dogs, cats, and rats. Renal MR were stimulated by increased ureteral pressure and renal CR by retrograde ureteropelvic perfusion with 0.9 M NaCl at unchanged ureteral pressure. In the dog, renal MR stimulation results in an increase in ipsilateral afferent renal nerve activity (ARNA) and contralateral efferent RNA (ERNA) and a contralateral renal vasoconstriction. Mean arterial pressure (MAP) is unchanged. Renal CR stimulation is without effect. In the cat, renal MR and CR stimulation increases MAP and either increases or decreases contralateral urine flow rate and urinary sodium excretion at unchanged renal perfusion pressure. In the rat, renal MR and CR stimulation increases ipsilateral ARNA, decreases contralateral ERNA and increases contralateral urine flow rate and urinary sodium excretion. The magnitude of the renorenal reflex responses is related to the magnitude of the stimulation. Furthermore the renorenal reflex responses are attenuated in spontaneously hypertensive rats (SHR). We conclude that there is a species difference in the nature of the renorenal reflex responses to renal MR and CR stimulation. The attenuated renorenal reflexes in SHR might contribute to their hypertension by promoting increased ERNA and sodium retention.