Rest and exercise first pass radionuclide ventriculograms were obtained in 62 morbidly obese subjects (56 women, six men, mean age 38 years, mean weight 269.2 ± 46.0 lb, mean height 65.2 ± 3.1 in., mean Body Mass Index 44.5 ± 6.2 kg/m2, mean excess body weight 134.1 ± 41.1 lb) scheduled for vertical banded gastroplasty. Fifty-six percent demonstrated exercise-induced wall motion abnormalities mimicking coronary disease, compared to 12% of controls (p = 0.03). No subject with exercise-induced abnormalities had coronary disease at cardiac catheterization although only those with an anginal chest pain history underwent angiography. Twenty-six percent demonstrated resting left ventricular systolic dysfunction as manifested by a reduced resting left ventricular ejection fraction (<0.50). Thirty-one percent of these patients demonstrated exercise-induced abnormalities, versus 65% of morbidly obese subjects with normal resting ejection fractions (p = 0.04). Obesity-induced left ventricular hypertrophy with associated reduced coronary vasodilator reserve could explain the abnormalities. Six month post-gastroplasty follow-up radionuclide ventriculograms show group normalization of the resting left ventricular ejection fraction in those with preoperative dysfunction, possibly due to left ventricular unloading with some regression of hypertrophy.