The hemodynamics in the patients undergoing craniotomy was studied to evaluate the interaction of cardiovascular effects of calcium blocking drugs (nicardipine NCR or diltiazem DL) and those of inhalation anesthetics (0.6% isoflurane Iso or 0.9% sevoflurane Sevo). (Group I = NCR alone, Group II = NCR+Iso, Group III = NCR+Sevo, Group IV = DL alone, Group V = DL+Iso, Group VI = DL+Sevo) Anesthesia was maintained with neuroleptanesthesia (N2O 60%). A 30% reduction in systolic blood pressure was achieved and this was maintained for 60 minutes in each groups. The following effects were observed during induced hypotension. 1) Heart rate increased in the group I and II, but decreased in the group IV, V and VI. 2) Cardiac output increased in the group I and II, but significantly decreased in the group VI. 3) Systemic vascular resistance and left ventricular stroke work decreased in all the groups. 4) Pulmonary vascular resistance decreased slightly in all the groups. 5) Cardiac arrhythmias were observed in 4 cases of the group IV and VI. These results suggest that the presence of Iso or Sevo at low concentrations does not have a marked effect on the pharmacologic action of NCR or DL in humans.