Ketanserin is a serotonin (S,) Mocker that reduces blood pressure (BP) in patients with essential hypertension preferentially by a reduction of peripheral vascular resistance. Heart rate is generally not affected or slightly reduced. When given in monotherapy on a 40 mg hid regimen, ketanserin reduces diastolic BP as effectively as metoprolol 100 mg bid or hydrochlorotiazide 25 mg bid The incidence of adverse reactions is low and comparable to these reference drugs. A satisfactory BP control is provided over a 24-h interval on a 40 mg bid dosage schedule, and the effect is maintained on a long-term basis, ie, 2 years. The response seems to be more marked in older patients, which may he due to an augmented platelet serotonin release and a vascular hypersensitivity in this age group. The future usefulness of ketanserin, as well as any other antihypertensive agent, will depend on its ability to prevent organ damage, as well as its ability to provide “quality of life” for the patient.