The hemodynamic effects of dimetofrine hydrochloride were investigated in dogs and children. Dimetofrine at dose of 0.5mg/kg was injected intravenously after induction of hemorrhagic hypotension in seven mongrel dogs. Thereafter hemodynamic effects and tissue oxygenation were observed for 20 min and compared to the data obtained in five mongrel dogs that received 7ug/kg/min of dopamine after hemorrhagic hypotension. The clinical study was performed in seven children who received open heart surgery. Dimetofirne at dose of 1.5mg/kg was injected intravenously during emergence from cardiopulmonary bypass and hemodynamics were observed. The followings are the results we obtained: 1) Dimetofrine resulted in rise in systolic and diastolic blood pressure, and mean arterial pressure in experimental and clinical study. Elevation of diastolic blood pressure was more remarkable than that of systolic blood pressure. 2) The maximum elevation of mean arterial pressure was noticed immediately after 1V bolus of dimetofrine;74.7% in animal and 69.2% in human. Through the experimental procedure, these elevations were maintained, but statistical significances were present until five min after dimetofrine. 3) Dimetofrine showed decreasing tendency in heart rate for 7.5% min in animal and all the time in human. 4) Coronary perfusion pressure was increased by 29 to 64% after 1V injection of dimetofrine. 5) Dimestofrine resulted in increase fo arterial oxygen tension and decrease of AaDO2 clinically. 6) Intravenous infusion of dopamine at rate of 7ug/kg/min resulted in small increase of mean arterial pressure, but no change in heart rate. In conclusion, pressor effect and negative chronotrople effect of dimetofrine were more remarkable, compared to 7ug/kg/min cf dopamine. Dimetofrine is believed to be the adequate pressor to improve myocardial oxygen supply, tissue oxygenation and blood pressure, and decrease the heart rate.