Transpyloric flow is the final step in gastric emptying prior to intestinal absorption of nutrients and medications. The details of this process are still incompletely understood. Transpyloric flow is bi-directional, contrasting with the general perception of solely forward flow implied by studies of gross gastric emptying. The degree to which the patterns of bi-directional transpyloric flow reflect emptying of meals of varied physicochemical composition, its mechanical determinants and effect on delivery of oral medications have been evaluated by the studies presented in this thesis.