The renal vasodilatating properties of tertatolol demonstrated in animals have been confirmed in man. In a first study [Paillard et al., 1986], tertatolol (T) 5 mg and propranolol (Pr) 160 mg (SR) were given orally for 15 days to 2 groups of 9 patients with essential hypertension. Glomerular filtration rate (GFR), measured by inulin clearance and renal plasma flow (RPF) measured by PAH clearance increased in T group (+8.9%, p = 0.038 and +13.0%, p = 0.007, respectively) and decreased in Pr group (-2.8%, NS and -13.4%, p < 0.001, respectively). Two clinical pharmacology studies [Leeman et al, 1986; Nitenberg et al, 1990] have shown specific and selective effects of tertatolol on the renal vasculature. In 8 hypertensive patients with chronic renal failure, the effects of tertatolol 5 mg were evaluated before and after 3 months of treatment on GFR using inulin clearance, and RPF, using PAH clearance [Hannedouche et al, 1991]. After 3 months of treatment, GFR and effective RPF increased significantly by 10 and 13%, respectively, whereas RVR decreased by 16% and the filtration fraction was unchanged. In summary, tertatolol 5 mg, contrasting with other beta-blockers, possesses a selective effect on the renal circulation beneficial to hypertensive patients. The mechanisms of this renal vasodilatation are not fully understood but might involve renal 5-HT<sub>1A</sub> receptor stimulation.