To compare the efficacy of intravenous diltiazem vs nitroglycerin in patients with unstable angina, we conducted a prospective, single blinded study enrolling 45 patients, 24 of them received diltiazem and 21 nitroglycerin. We considered drug failure if the patient experienced two or more anginal episodes or if one of them was longer than 30 minutes. There was a good response in 19 of 24 patients (79%) of the diltiazem group and 17 of 21 (81%) in the nitroglycerin group. Only one of the 5 non-response patients in the diltiazem group that was crossed to nitroglycerin was controlled, in opposition to the 4 patients crossed to diltiazem that were controlled all of them (p less than 0.05). Both drugs significantly (p less than 0.01) reduced systolic and diastolic blood pressure, but there was not difference between the two groups. Heart rate and double product decreased only in the diltiazem group (p less than 0.05). We did not find notorious side effects. We concluded that diltiazem is an alternative to nitroglycerin in patients with unstable angina.