Evidence is accumulating that epidural technique to provide postoperative analgesia is able to decrease perioperative morbidity particularly in obese patients. We investigated the effect of body mass index on efficacy of thoracic epidural analgesia by measurement of pulmonary function tests, arterial blood gases, hemodynamics, visual analogue scale, and total local anesthesia requirements. Sixty patients undergoing open upper abdominal surgeries as patients were divided according to their body mass index into obese and nonobese groups. We concluded that the efficacy of thoracic epidural analgesia doesn’t change with increase the body mass index and the use of thoracic epidural analgesia, should be considered for the morbidly obese patients.