Circulatory variables and arterial partial pressure for oxygen (PaO2) were compared in 91 anesthetized patients who received infusions of either nitroglycerin (TNG) or nitroprusside (SNP) to induce hypotension for the purpose of decreasing intraoperative blood loss. At comparable systolic arterial blood pressures, the mean and diastolic arterial blood pressures were significantly higher with TNG. Electrocardiographic changes suggestive of ischemia occurred in 18 patients who received SNP, whereas none were detected in patients given TNG. Both drugs significantly decreased PaO2 and rate-pressure product, an indirect index of myocardial oxygen consumption. No untoward response to TNG occurred. No clinical evidence of myocardial infarction, renal damage, or cerebral vascular complication was encountered in the postoperative period in any patient. Thus, TNG is an effective hypotensive drug that may prove superior to currently available agents.