Summary This study was designed with the primary purpose of testing two hypotheses: (1) Animals placed in a severe conflict situation for a relatively long period of time (30 days) would develop gastrointestinal changes which would lead to the formation of gastric ulcers; (2) animals placed in a chronic fear-producing situation for a relatively long period of time (30 days) would develop gastrointestinal changes which would lead to the formation of gastric ulcers. To test these hypotheses, 90 rats were divided into 6 split-litter groups (insofar as possible), of equal size, and each of these groups was placed in a different experimental situaton. Two of these situations subjected the animals to an approach-avoidance type of conflict; two situations were fear producing, with food and water deprivation being present in one of these but not in the other; and two were control situations involving only food and water deprivation or food and water deprivation plus cephalic phase (seeing and smelling food and water). During testing, 30 of the animals were on a 46-hour deprivation schedule and 45 animals were on a 47-hour deprivation schedule. Fifteen animals in one of the fear-producing situations were not deprived of food and water. With respect to the two hypotheses the following conclusions were reached: A significantly greater number of animals in the two conflict situations developed lesions in the rumen of their stomachs than the comparable animals in the two control situations. This evidence was interpreted as confirming the first hypothesis. A significantly greater number of animals in one of the fear-producing situations (also involving deprivation) developed lesions in the rumen of their stomachs than the animals of the appropriate control situation. This evidence was interpreted as supporting the second hypothesis. A significantly larger number of animals of the fear-producing situation (in which deprivation was present) had stage 2 changes than those of the fear-producing situation in which food and water was always present. These results were interpreted as indicating that having the animals on a severe food- and water-deprivation schedule seemed to be a necessary prerequisite for the occurrence of the lesions in the rumen of the stomach. The presence of the cephalic phase variable (present in two situations) was associated with a slight but insignificant increase in the relative frequency of lesions in the rumen of the stomach. The interpretation here was that the more severe gastric trauma observed in these situations could not be attributed to the presence of the cephalic phase variable since similar pathological changes were observed in the situations where this variable was not present. Conflict and chronic fear as induced in this study seem to be associated with similar frequencies of pathological changes. Having animals on 47-hour food- and water-deprivation resulted in more severe gastric trauma than having animals on 46-hour deprivation. Again these results seem to indicate that more severe pathological changes were associated with a more severe food- and water-deprivation schedule. A significantly greater number of gridcrossing attempts were made by the animals of the conflict situation in which they could not see any food and water containers than were made by the animals of the conflict situation in which they could see the food and water containers. No interpretation was made concerning these unexpected results. Animals of one of the conflict situations and one of the fear-producing situations defecated significantly less than the animals of the respective control situations. The interpretation made here was that although defecation may be a valid measure of emotionality when an animal is placed in a situation for only a short period of time, it may not be a valid measure when an animal is placed in a similar situation for a longer period of time. No significant difference in the amount of weight lost by the animals of the various situations, involving food and water deprivation, was found. These results seem to indicate that the pathological changes observed in this study cannot be attributed to the amount of weight lost by the animals while in the experimental situations. The proportion of animals of either sex observed as having lesions in the rumen of their stomachs was approximately equal. The age of the animals seemed to be of no significance as far as severity of gastric trauma was concerned. It was postulated that either an excessive volume of gastric juice or an increase of its acidity brought about the lesions, and that these gastrointestinal changes occurred to a large extent as a result of the induced conflict or fear states.