We have investigated the effects of a novel calcium antagonist, fantofarone (SR 33557) on myocardial oxygen consumption (MO2C) and coronary blood flow in anaesthetized dogs during periods of normal and elevated heart rate. 25 micrograms/kg i.v. fantofarone induced a transient increase in coronary blood flow (+25% after 2 min; p < 0.05) and a more sustained decrease in MO2C (-50% after 5 min; p < 0.05). During the periods of pacing, these alterations on cardiac function were not evident. Administration of 50 micrograms/kg i.v. resulted in similar modifications of cardiac function; however, these changes were apparent for a longer duration. Coronary blood flow was still significantly elevated by 29% 2 min after drug administration (p < 0.01) and MO2C was reduced by 67% after 5 min (p < 0.01) and by 56% after 30 min (p < 0.05). Most importantly, a significant decrease in MO2C was observed during the pacing periods (32% after 10 min; p < 0.01). Thus fantofarone can significantly modify cardiac function and in particular, decrease MO2C consumption during periods of elevated heart rate.