The gastric emptying of a liquid test meal containing 99Tcm-sulphur colloid was studied with a gamma camera in 24 duodenal ulcer patients. Studies were made before surgery, randomly chosen between truncal vagotomy with pyloroplasty and parietal cell vagotomy, and six weeks and one year after. Large variations in the emptying patterns were observed both between patients and in the same patients. No consistent change in the distribution of patterns were found between the three observation times and between the two surgical procedures. An initial rapid emptying was found in several studies and was observed both before and after operation and did not seem to be related to type of surgical procedure or to individual patients. The method applied did not allow a detailed study of this initial phase, which appears to be of a higher significance for the over-all emptying characteristics than the late exponential emptying, on which earlier investigators have been focused.