The calcium antagonist, diltiazem is effective in the treatment of patients with various types of angina pectoris, as well as with essential and renovascular arterial hypertension. Sustained-release diltiazem in dose of 180 mg once daily is effective as sustained-release diltiazem in dose of 90 mg twice daily. Besides, in patients with stable angina pectoris and essential arterial hypertension the monotherapy with sustained-release diltiazem in dose of 180 mg is similarly effective as beta blockers and thiazide diuretics. However, monotherapy with sustained-release diltiazem is at least effective as monotherapy with sustained-release verapamil. Comparative clinical investigations showed that diltiazem is more effective than propranolol in decreasing ischemic attacks, whereas the risk of bradycardia is smaller. On the other hand, nifedipine (dihydropyridine calcium antagonist) is more effective than diltiazem in lowering ischemic electrocardiographic changes, incidence of attacks and improving working capability. The efficacy of diltiazem, nifedipine and verapamil is similar in the treatment of patients with spastic angina pectoris, whereas the least effective is propranolol. As far as the arterial hypertension is concerned, clinical investigations showed that the efficacy of diltiazem and nifedipine is similar. Side effects are relatively rare (1.8-9.6% patients) and depend on the dose (nausea, fatigue, dizziness, headache and itching).