This trial evaluated whether the intravenous injection of an ultrasound contrast agent (Infoson) facilitates the assessment of systolic function in 40 low-echogenic patients undergoing low-dose (4 mcg/kg/min) dopamine echocardiography. Interobserver difference in calculated ejection fraction at entry was > 10%. Echocardiographic monitoring was performed in the apical 4-chamber view at four intervals: baseline, no contrast; first Infoson injection; dopamine infusion, no contrast; dopamine infusion+second Infoson injection. The left ventricle was divided into 5 segments and analysis was performed by two blinded observers. Wall motion abnormalities, ejection fraction and the confidence in detecting the endocardial border, were assessed. Infoson provided adequate left ventricular opacification in 90% of the injections, with a significant improvement in endocardial border detection. The interobserver variability of ejection fraction measurements was significantly reduced. The probability of attaining concordance between the investigators on wall motion assessment improved significantly. These results suggest potential applications in stress echocardiography.