Volume, pH, and total acidity of the basal and of the stimulated gastric secretion were measured in guinea-pigs before, and at appropriate intervals after, x-irradiation to the stomach area. A great reduction of the stimulated acidity and acid output was found. It reached a maximum between the second and the fourth week after irradiation. Thereaftcr the total acidity increased gradually. but, 56 weeks after irradiation, it still remained significantly below the normal (p < 0.05). The volume was lowered to a lesser extent.Scand J Gastroenterol Downloaded from informahealthcare.com by University of Calgary on 02/02/15For personal use only.