1. The pharmacokinetics of intravenous and oral atenolol (50 mg) in six healthy volunteers was studied. Plasma, saliva and urine were collected up to 24 h after each dose. 2. There was no significant difference in atenolol half-life when administered by the two routes. Bioavailability of the orally administered atenolol was 50%. 3. Atenolol levels in saliva required about 2 h to reach equilibrium with plasma drug levels. 4. A comparison between the pharmacokinetics and pharmacology of atenolol was made in twelve healthy subjects. 5. Dose-independent pharmacokinetics were observed. Reductions in resting heart rate and arterial blood pressure were proportional to either the logarithm of dose or area under the plasma concentration time curve or cumulative urinary atenolol excretion. 6. Plasma elimination half-life in five subjects with renal failure was prolonged.