Determinations of gastric emptying time (GET) and small intestinal transit time (SITT) are useful in detecting gastrointestinal motility disorders and partial obstructions of the pylorus or small intestine. Barium-impregnated, polyethylene radiopaque spheres with diameters of 1.5 mm and 5.0 mm have been developed for quantitative assessment of gastrointestinal transit. The purpose of this study was to evaluate GET and SITT using these radiopaque spheres in 10 healthy cats. The cats were randomly assigned to 1 of 3 treatment groups: fasted, fed, and fed plus sedation (acetylpromazine maleate 0.10 mg/kg subcutaneously). A repeated measures study design was used. The mean GETs of 50%, 75%, and 90% of the 1.5-mm and the 5-mm spheres in the unfed cats were 0.36, 0.58, and 0.74 hours, and 0.41, 0.68, and 1.02 hours, respectively. These values were significantly (P < or = .05) more rapid than the GETs of 50%, 75%, and 90% of the 1.5-mm and 5-mm spheres of either the sedated fed cats (4.39, 5.68, 6.65 and 5.15, 5.99, 6.91 hours) or the unsedated fed cats (6.43, 8.12, 9.06 and 7.49, 8.49, 9.22 hours). The mean GETs of 50% and 75% of the 1.5-mm and 5-mm and of 90% of the 1.5-mm spheres were significantly (P < or = .05) more rapid in sedated than in unsedated fed cats. The GET of 50% of the 1.5-mm spheres was significantly more rapid (P < or = .05) than that of the 5-mm spheres in the fed cats. The mean SITTs, which ranged from 2.25 to 3.05 hours, were not significantly different (P > .05) among the treatment groups or between the 1.5-mm and 5-mm spheres. The GET of spheres given to fasted cats is significantly more rapid than that of fed cats. Subcutaneous injection of acetylpromazine speeds GET in fed cats. The SITT of small and large spheres was not influenced by feeding or by acetylpromazine injection.