The effects of dilevalol, a new beta-adrenergic blocking agent with beta-agonism, on renal function were determined in two groups of patients. Patients in group 1, all with normal renal function, received either dilevalol or atenolol. Patients in group II, all with impaired renal function, received either dilevalol or metoprolol. Parameters of renal function determined before and after chronic oral treatment included glomerular filtration rate (GFR), effective renal plasma flow, filtration fraction, mean arterial pressure (MAP), renal blood flow, and renal vascular resistance. Dilevalol lowered MAP by 14 mm Hg (P less than 0.005) in group I and 25 mm Hg (P less than 0.01) in group II but had no effect on other parameters of renal function, at either peak or trough drug levels. Atenolol and metoprolol also lowered MAP by 11 mm Hg (P less than 0.01) and 15 mm Hg (P less than 0.05), respectively. Atenolol reduced GFR by 23% at peak drug level, an effect that was partially ameliorated at trough drug level. The effect of atenolol on GFR appeared to vary as a function of baseline renal function in that greater reductions were seen in groups of patients with increasing baseline GFR. Metoprolol significantly decreased renal vascular resistance by 17% (P less than 0.05). These data suggest that dilevalol effectively lowers blood pressure in hypertensive patients with normal or compromised renal function with no negative impact on parameters of renal function.