Eleven patients with anterior myocardial infarction less than six hours old underwent intraaortic balloon pumping (IABP) in an attempt to control injury. Direct hemodynamic measurements excluded shock. Response to therapy was judged individually by comparison to a one-hour pretreatment period. There was no parallel control group. Five patients responded with an 84% fall in ST elevation in one hour, with preservation of precordial R waves and good ventricular function. In contrast, six patients responded poorly, with a 40% fall in ST elevation in one hour, Q wave development and poorer residual left ventricular function. Coronary angiography demonstrated a significant correlation between response and presence or absence of complete left anterior descending coronary artery occlusion. Early use of IABP in anterior myocardial infarction may interrupt injury, though in this series only in cases with residual left anterior descending patency.