Epicardial fat assessed using echocardiography is associated with abdominal visceral adipose tissue and cardiovascular risk factors. Because of its location, epicardial fat may directly affect the coronary vasculature and myocardium through local secretion of bioactive molecules. This study examines the effects of weight loss after bariatric surgery on epicardial adipose tissue in patients with severe obesity. Clinical data and echocardiograms of 23 patients with severe obesity who had echocardiograms recorded before and 8.3 +/- 3.7 months after undergoing bariatric surgery were retrospectively reviewed. Epicardial fat thickness was measured as the hypoechoic space anterior to the right ventricle in both the parasternal long- and short-axis views, and an average was obtained. At baseline, patients had increased epicardial fat compared with normal-weight controls matched for age, gender, and ethnicity (5.3 +/- 2.4 vs 3.0 +/- 1.1 mm, p <0. 001). Epicardial fat thickness was associated with the patient's initial weight in severely obese patients (r = 0.51, p = 0.011). Patients lost an average of 40 +/- 14 kg after surgery. Epicardial fat thickness decreased from 5.3 +/- 2.4 to 4.0 +/-1.6 mm (p = 0.001). Change in epicardial fat correlated with initial epicardial fat thickness measured using echocardiography (r = 0.71, p <0.001). In conclusion, epicardial fat thickness decreases in severely obese patients who have substantial weight loss after bariatric surgery. Measuring epicardial fat thickness using echocardiography may be useful to monitor visceral fat loss with weight reduction therapies.