In 196 patients suffering from duodenal ulcer disease, gastric emptying was measured by use of a radiolabelled testmeal. The measurements were performed during the digestive phase of gastric activity. On the basis of the predominantly exponential form of gastric emptying the T 1/2 was chosen as a measure of this function. The results were: 1. In 50 subjects without gastrointestinal disease the median T 1/2 was 59 min, mean and standard deviation were 58.8 +/- 9.13 min; 2. the T 1/2 value in 71 patients with deformed duodenal bulb (median 53 min) was significantly accelerated if compared to the normal value (2 p less than 0.01); 3. T 1/2 in 88 patients with deformed bulb combined with acute ulcer (median 49 min) was shorter than T 1/2 of the normal subjects (2 p less than 0.001); 4. T 1/2 in 25 patients with pyloric stenosis (median 102 min) was longer than normal value (2 p less than 0.001).