The effects of o-methyldauricine ( OMD ) , a derivative of dau-ricine, 2.5 & 5 nig/kg given intravenously on ECG & haemodyna-mics were studied in 14 anaesthetized dogs.OMD significantly decreased systolic & diastolic blood pressure dose-dependently, accompanied by a decrease in total peripheral resistance, an increase in strok volume & a slight increase in PEP/LVET. These haemodynamic effects are similar to those of dauricine. It produced a decrease in heart rate & no changes of mean pulmonary artery pressure & pulmonary capillary wedge pressure. 2.5mg/kg of OMD did not influence ECG significantly; 5 mg/kg of that slightly prolonged PR interval & did not alter QRS width & QTc interval significantly. Comparing with the results reported previously about dauricine the data suggest that OMD is similar to dauricine in hypotensive effect & different in effects on ECG from dauricine that prolonged PR interval & QRS width significantly.