Postprandial gastric emptying and gallbladder contraction were assessed in 14 healthy subjects by means of ultrasonography after oral administration of a semi-liquid test meal (250 ml, 1450 kJ). For this purpose, cross-sectional areas of the gastric antrum and gallbladder volume were calculated and recorded over a period of 120 minutes using an annular-array-transducer. The semi-liquid test meal allowed suitable sonographic measurement of cross-sectional areas of the antrum in all 14 subjects. Mean half-time of gastric emptying was 47 minutes (range 17-72 minutes). Mean peak gallbladder contraction was 36% (range 17-60%) of initial volume and mean time to peak contraction was 65 minutes (range 20-120 minutes). The method described was found to be a practical and reliable procedure for the investigation of postprandial gastric emptying and gallbladder contraction. It is therefore of potential interest for application to a variety of clinical questions. A minor drawback involves the relative length and variability of time required for testing, owing to the wide range in the time-course of gastric emptying and gallbladder contraction across subjects. Normal ranges for defined test meals must be established in large control groups.