Metabolizable energy (ME) requirements for pregnant swine were estimated by the factorial method on the basis of the proposed model and the available data as well. The results indicated that the ME requirements estimated in the present study were lower by approximately 15% and 9% at 20 kg and 40 kg net weight gain during pregnancy, respectively, as compared with those recommended by the Agricultural Research Council (1981). The daily ME requirements of pregnant swine increased at the rates of 21.9 kcal, 63.8 kcal and 125.4 kcal with an increase of 1 kg in body weight at mating, 1 kg in net weight gain during pregnancy and a head in the number of fetus, respectively. Such information should be highly useful in managing the feeding of pregnant swine. However, the reproductive performance for a long-term must be carefully examined in pregnant swine reared with the amount of ME proposed in the present study.