Experiments were performed in which the effects of two β-blockers, tertatolol [dl-(hydroxy-2’-t-butyl-amino-3’-propyloxy)-8-thiochroman hydrochloride] and propranolol, on mean arterial pressure (MAP), heart rate (HR), and renal function were studied in the conscious sodium-replete dog. In all experiments renal function was evaluated from the effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) assessed respectively by measurement of p-aminohippurate and creatinine clearances. These parameters were measured during two 30-min control periods, after which two further measurements were performed over a similar time period, after intravenous administration of either propranolol (0.5 mg·kg-1; n = 8) or tertatolol (0.05 mg·kg-1; n = 8), these two doses being of equivalent β-adrenoceptor antagonist activity. Administration of propranolol and tertatolol did not change MAP but induced a significant and comparable decrease in HR. After propranolol a significant decrease in ERPF was observed, without any change in GFR or sodium excretion. In contrast, administration of tertatolol resulted in no modification of ERPF, a slight but significant increase in GFR, and a significant increase in sodium and potassium excretion. These results suggest that tertatolol and propranolol though acting similarly on systemic parameters have different effects on renal hemodynamics in the conscious dog.