The nutritional and energetic value of a pig's diet depend on the rate of starch digestion. At the moment, however, the reasons behind variation in in vivo digestion rates of different starches are not fully understood. The main aim of this thesis was to quantify the contribution of intrinsic starch structure, feed processing, and digesta passage behaviour on the kinetics and mechanisms of starch digestion in the upper gastrointestinal tract (GIT) of pigs. This thesis describes how the difference between the in vitro and in vivo situation is dominated by the initial rate of starch digestion, which was higher in vivo than in vitro. Gastric starch digestion and predigestion seem to contribute to the more rapid initial starch digestion in vivo and is a key factor in an accurate prediction of starch digestion rates.