To assess whether or not a persistent antral response to meat extract stimulation is an indication of incomplete vagotomy, 29 patients with a duodenal ulcer who underwent operation had preoperative and postoperative acid studies as well as postoperative Hollander tests. In the preoperative tests, two groups of patients were delineated--antral and nonantral responders. Postoperative Hollander tests revealed three positive responses; in two patients with an early positive response, meat extract led to a significant increase in acid and gastrin response. In the patient with a late positive Hollander test, there was no response to meat extract. In two patients with proved stomal ulcers and negative Hollander tests, meat extract led to a significant increase in acid and gastrin output. These results suggest that an antral acid and gastrin response to meat extract indicate an incomplete vagotomy.