Dobutamine stress echocardiography was performed in 56 consecutive patients, mean age: sixty-two +/- twelve years. Twenty-two patients had an idiopathic dilated cardiomyopathy (group 1) and 34 had angiographically proven ischemic dilated cardiomyopathy (group 2). Wall motion score index and left ventricular ejection fraction were determined at baseline, 5 micrograms/kg/min, peak, and ten minutes after stepwise dobutamine infusion. Worsening or no change in global wall motion score was observed in 9 group 2 patients (26%) and 1 group 1 patient (5%, P = .07). No significant difference was observed with regard to wall motion score index decrease between baseline and peak dose. Left ventricular ejection fraction increase during dobutamine infusion was comparable in both groups. Thus, an ischemic response was observed more often in the coronary artery disease group, yielding a good specificity and positive predictive value although sensitivity was low. However, left ventricular function improvement did not help to discriminate patients with or without significant CAD.