The purpose of this study was to evaluate the effects of verapamil on hemodynamics and pulmonary gas exchanges during isoflurane-N2O-O2(FIO2, 50%) anesthesia. Hemodynamic measurements and arterial and mixed venous blood gas analyses were made in thirteen healthy patients immediately before (control) and at 1, 5,10min after 5mg of intravenous verapamil administration as single bolus. 1) Verapamil produced a rapid and transient reduction of 15% in mean arterial pressure resulting from a decrease in systemic vascular resistance. 2) Heart rate and cardiac index increased by 14%, 9% respectively only immediately after i.v. verapamil injection and restored thereafter toward control values. 3) SVI, MPAP, PCWP, PVR and CVP revealed only minor changes. 4) Verapamil did not cause any significant changes in intrapulmonary shunt. These findings suggest that during isoflurane-N2O-O2(50%) anesthesia verapamil might safely be used, even in the presence of ventilation/perfusion inequalities, (i.e. lung disease, one lung anesthesia) provided patient has good cardiovascular reserve.