Abstract. Acute gastric dilatation occurs sporadically in laboratory-housed nonhuman primates. Clinical histories often include chronic drug administration, food restriction, accidental overfeeding, and prior anesthesia. Monkeys may be found dead or may have clinical signs of colic, abdominal distention, and dyspnea. Death in untreated cases is due to impaired venous return and cardiopulmonary failure. Gastric distention with fermented gaseous ingesta and congestion of the abdominal viscera are the predominant lesions. The cause of acute gastric dilatation is unknown, but it probably is multifactorial. Two principal factors seem to be intragastric fermentation associated with Clostridium perfringens, and abnormal gastric function.Acute gastric dilatation occurs sporadically in laboratory-housed nonhuman primates and there is a high mortality rate in untreated cases. The cause of this condition has not been investigated in controlled laboratory studies, but the clinical syndrome and the lesions are well characterized [2,7,11,[13][14][15][16]. In this paper, reported cases of acute gastric dilatation in nonhuman primates are reviewed and compared to the condition in 2 1 monkeys necropsied at a university medical facility.Acute gastric dilatation was first reported in eight macaques in 1967 [2]. Subsequently, there have been cases in both Old and New World monkeys [4,7,9,11,[13][14][15][16]. The clinical syndrome and lesions of acute gastric dilatation are remarkably consistent in all reports, including ours (see Results). The pathogenesis of acute gastric dilatation has not been elucidated, but there seem to be several common predisposing factors: dietary manipulation, microbial fermentation of ingesta, and prior anesthesia. Intercurrent disease rarely is present, although there was one report of acute gastric dilatation in a pet Ateles geoffroyi that also had rickets [7].The quantity and composition of monkeys' diets are important in the pathogenesis of acute gastric dilatation. Many monkeys with a history of food restriction in conjunction with behavioral experiments develop the syndrome following subsequent ad libitum feeding or overfeeding 111, 14, 151. Changes in feeding practice over 126