Diltiazem is a benzothiazepine derivative calcium antagonist available in several formulations, some of which enable once daily administration. The drug as monotherapy has demonstrated similar efficacy to diuretics in older patients with hypertension. Data comparing diltiazem with beta-blockers and angiotensin converting enzyme inhibitors are more limited, but available studies suggest at least comparable antihypertensive efficacy. Diltiazem as monotherapy or in combination with a beta-adrenoceptor-antagonist, isosorbide dinitrate, or another calcium antagonist, has demonstrated efficacy in patients with effort angina. The drug has also been used intravenously to terminate supraventricular tachycardias and to control the ventricular response to atrial fibrillation or flutter; it also appears to reduce the rate of early reinfarction in patients with non-Q-wave myocardial infarction. The most common adverse events during diltiazem therapy include headache, flushing, peripheral oedema and hypotension. Atrioventricular block although rare, is the most frequent serious adverse event related to diltiazem therapy and may be exacerbated by coadministration of beta-adrenoceptor antagonists, especially in the elderly. Thus, diltiazem appears to be an effective and well tolerated treatment for hypertension and angina in older patients and has shown promise as therapy for supraventricular tachycardias and as prophylaxis against early reinfarction in patients with non-Q-wave myocardial infarction.