In the present study, we investigated whether the intravenous injection of air-filled albumin microspheres (Infoson) as a contrast medium improves the echocardiographic quantification of left ventricular enddiastolic and endsystolic volumes, stroke volume, ejection fraction, and regional wall motion in patients with suboptimal endocardial border definition on echocardiography. In 30 adult patients, apical two and four chamber views were performed. In comparison to biplane cineventriculography enddiastolic and endsystolic volumes, stroke volume, ejection fraction, and regional wall function were assessed for heart cycles with and without left ventricular contrast. In comparison to biplane cineventriculography echocardiography underestimates enddiastolic (167+/-64 ml, 111+/-43; p<0.0001) and endsystolic volumes (77+/-63 ml, 54+/-40 ml; p<0.0002), stroke volume (90+/-25 ml, 57+/-17 ml; p<0.0001), and ejection fraction (58+/-16%, 55+/-14%; p<0.03). By contrast echocardiography ejection fraction (58+/-16%) agreed with the angiocardiographically measured ejection fraction. Furthermore, after contrast injection correlations improved between cineventriculography and echocardiography for the assessment of left ventricular enddiastolic volumes (without contrast r = 0.90, SEE = 19 ml; with contrast r = 0.93, SEE = 19 ml), endsystolic volumes (without contrast r = 0.94, SEE = 14 ml; with contrast r = 0.95, SEE = 15 ml), stroke volume (without contrast r = 0.63, SEE = 14 ml; with contrast r = 0.67, SEE = 14 ml), ejection fraction (without contrast r = 0.84, SEE = 8%; with contrast r = 0.88, SEE = 7%), regional wall motion (p<0.01) and its reproducibility (p<0.02). In adult patients with suboptimal endocardial border delineation intravenous contrast echocardiography improves the assessment of left ventricular ejection fraction, regional wall motion, and its reproducibility without severe side effects.