BACKGROUND/AIMS: Three dimensional (3-D) ultrasonography is definitely more accurate than conventional 2-D ultrasonography in volume measurement of intra-abdominal organs. However, its application in measuring gastric emptying time has been limited. Thus, we tried to measure gastric antral emptying time by using 3-D ultrasonography and compare with that by radio-scintigraphy. METHODS: We performed both 3-D ultrasonography and radio-scintigraphy on the same day in 23 healthy subjects. After overnight fast, the subjects ingested 500 mL of soup meal (84 Kcal) that had been pre-mixed with 1 mCi of technetium(99m). The half emptying time (T(1/2)) measured by 3-D ultrasonography was defined by the time when the gastric antral volume decreased to half. RESULTS: The mean T(1/2) of 23 healthy subjects measured by 3-D ultrasonography was 23.4 +/- 10.5 min, while that measured by scintigraphy was 28.4 +/- 14.4 min. The difference (p=0.11 by paired t-test) between the two methods was not significant. Moreover, no significant correlation of T1/2 between the two methods (r=0.361, p=0.09) was observed. CONCLUSIONS: Measuring gastric antral emptying time with 3-D ultrasonography may be useful but require further validation studies and advance in technology.