Gastric ulcer following gastric "freezing" for the treatment of peptic ulcer is a significant and alarming complication of this therapeutic modality.1 This study was designed to determine the causative factors of this complication and to explore measures for its prevention. Method In this study, 70 mongrel dogs, 10 to 20 kg (22 to 44 lb) in weight were used. Under intravenous nembutal anesthesia, a laparotomy was performed, and needle thermistors were implanted in the submucosal layer of the gastric fundus, anterior and posterior wall of the body of the stomach, and the anterior gastric antrum. The systemic temperature was checked by rectal thermometer. In some of the animals three additional thermistors were attached to the surface of the balloon in the stomach. Using a hypothermia unit, the animals were subjected to gastric freezing, as outlined by Wangensteen, for a period of 50 minutes.2,3 Inflow (machine) temperature varied between