The relationship between indenolol (an investigational agent) plasma levels and the drug's effect on blood pressure and heart rate was investigated after single and repeated once daily administration at two dosage levels (60 mg and 120 mg) in two different groups of patients with first or second stage hypertension, according to the World Health Organization classification. The pharmacokinetic data were indicative of a first order absorption-elimination curve; time of maximum plasma levels was 1.5 to two hours, and elimination half-life was four hours. The drug did not accumulate in the central compartment after repeated administrations. A long-lasting decrease of both resting and isometric exercise systolic pressure values was recorded after acute indenolol administration. Diastolic pressure was affected only by repeated administrations. The lower dose (60 mg daily) of indenolol did not affect heart rate, whereas the higher dose (120 mg daily) decreased this parameter. A steady state of pressure values and heart rate was reached after 14 days of once daily treatment.