A neonate initially presented with heart failure, with severe cardiac dysfunction confirmed by echocardiography, at 3 days of age. Blood pressure at presentation was in the high normal range. It was not until there was a rapid improvement of left-ventricular function on intravenous milrinone that the infant was noted to be hypertensive on day of life 7. It is noteworthy that milrinone, a drug with vasodilator and inotropic properties, paradoxically unmasked hypertension by rapidly improving left-ventricular function. Subsequent work-up showed the etiology of hypertension to be left renal artery stenosis. We present this case to alert clinicians to the rarer causes of left-ventricular dysfunction and to point out that its etiology, i.e., hypertension, may not be apparent until there is improvement in the systolic function of the left ventricle.