The factors influencing appetite in humans are poorly understood. There is a weak relation between appetite and gastric emptying in normal subjects. Recent studies have shown that fasting and postprandial antral areas increase in patients with functional dyspepsia compared with normal subjects. We evaluated the hypothesis that antral area, and hence antrat distention, is a significant determinant of postprandial fullness. Fourteen normal subjects had simultaneous measurements of gastric emptying by scintigraphy and antral area by ultrasound after ingestion of 350 mL 20% glucose. Fullness and hunger were assessed by visual analog scales. Measurements of the gastric-emptying half time ([t.sub.1/2]) by scintigraphy and ultrasound were not significantly different (129.6 [+ or -] 11.8 min compared with 115.6 [+ or -] 11.4 min). Fullness increased (P [is less than] 0.001) and hunger decreased (P [is less than] 0.001) after the drink. Both fullness and the magnitude of the increase in fullness after the drink were related to antral area (r [is greater than] 0.56, P [is less than] 0.05), the increase in antral area (r [is greater than] 0.59, P [is less than] 0.05), and the scientigraphic content of the distal stomach (r [is greater than] 0.57, P [is less than] 0.05), but not to the ultrasound or scientigraphic [t.sub.1/2] values. In contrast, hunger and the magnitude of the decrease in hunger after the drink were not related to either antral area, the increase in antral area, or the rate of gastric emptying. We conclude that postprandial fullness, but not hunger, was closely related to antral distention in normal subjects. Am J Clin Nutr 1997;66:127-32.