Threonine is often the second limiting amino acid in most practical swine diets. Therefore, the threonine requirement of the high producing sow in lactation was determined in this study. Using a total of 419 C-15 PIC sows, the threonine requirement to minimize sow tissue breakdown was found to be 37.3, 40.0 and 38.9 g total threonine/d (28.7, 30.8 and 30.0 g digestible threonin/d) for parity 1, 2 and3+ sows, respectively. To maximize litter growth, the threonine requirement was found to be 36.6, 39.2 and 38.2 g total threonine/d (28.2, 30.2 and 29.5 g digestible threonine/d) for parity 1, 2 and 3+ sows, respectively.