Physicochemical properties of diets are believed to play a major role in the regulation of digesta transit in the gastro-intestinal tract. Starch, being the dominant nutrient in pig diets, strongly influences these properties. We studied transport of digesta solids and liquids trough the upper gastro-intestinal tract of 90 pigs in a 3x3 factorial arrangement. Dietary treatments varied in starch source (barley, maize, high-amylose maize) and form (isolated starch, ground cereal, extruded cereal). Mean retention times (MRT) of digesta solids ranged 129-225 min for the stomach and 86-124 min for the small intestine (SI). The MRT of solids consistently exceeded that of liquids in the stomach, but not in the SI. Solid digesta of pigs fed extruded cereals remained 29-75 min shorter in the stomach compared with pigs fed ground cereals (P<0.001). Shear stress of whole digesta positively correlated with solid digesta MRT in the stomach (r=0.33, P<0.001), but not in the SI. The saturation ratio (SR), the actual amount of water in stomach digesta as a fraction of the theoretical maximum held by the digesta matrix, explained more variation in digesta MRT than shear stress. The predictability of SR was hampered by the accumulation of large particles in the stomach. In addition, the water holding capacity of gelatinised starch lead to a decreased SR of diets, but not of stomach digesta, which was caused by gastric hydrolysis of starch. Both of these phenomena hinder the predictability of gastric retention times based on feed properties.