The effects of four levels of dietary threonine (Thr) on growth performance, N retention and structure of the small intestine were studied in pigs from 13 to 22 kg of body weight (BW). Four diets were formulated to contain 6.46, 7.43, 8.37 and 9.32 g Thr. Each diet was fed to six pigs for 19 days and N balance was determined at 15 kg BW. Tissue samples of the small intestine were taken for histological and histochemical measurements. In pigs fed Thr-deficient diet, N retention (g per day) was lower than on diets containing 7.43 and 9.32 g Thr per kg. Tunica mucosa thickness and number of goblet cells (in villi and/or in crypts) containing neutral mucins were smaller on Thr-deficient diet than on other diets. It can be assumed that the level of dietary Thr amounting about 7.4 g per kg covers the requirement of piglets from 10 to 25 kg for rapid growth and maximal N retention as well as for supporting gut barrier function.