[13C]Acetate and [13C]octanoate breath tests were used to analyze the gastric emptying of liquids and solids in healthy controls and patients with functional dyspepsia both with and without cisapride. A standard test meal was labeled with either 150 mg [13C]acetate (liquid phase labeled in the water) or with 100 mg [13C]octanoate (solid phase labeled in the egg yolk). Six patients with dyspepsia and six healthy controls underwent a 4-hr breath test four times, ie, both the [13C]acetate and [13C]octanoate test with and without cisapride. Duplicate [13C]acetate or [13C]octanoate breath tests were performed in another 12 healthy controls in order to assess day-to-day variability of gastric emptying for liquids and solids. The mass spectrometric data were fitted to a power exponential function allowing mathematical analysis of half-emptying times and lag times. In patients with dyspepsia, gastric half emptying times of solids were significantly delayed as compared to the emptying of solids in the controls (203 +/- 41 vs 148 +/- 35 min; P < 0.05). With cisapride, gastric emptying of solids was significantly accelerated (P < 0.05) both in the patients (166 +/- 58 min) and in the controls (117 +/- 27 min). The gastric emptying of liquids did not differ in patients and controls, and cisapride had no effect on the emptying of liquids within the normal range. In the healthy controls, half emptying times both for liquids and solids were reproducible on the two different days (CVintra: 5.58% for liquids, 20.01% for solids).(ABSTRACT TRUNCATED AT 250 WORDS)