The present study was carried out to compare the reproductive performance and the serum concentrations of peptide and steroid hormones between the Landrace and the two-breed cross [(Large White ♂ x Landrace ♀) F₁] in the gilt from 15 days after mating to 10 days postpartum. Five gilts of the Landrace and the two-breed cross, respectively, were used for collection of blood samples. FSH, LH, prolactin, estradiol-173, progesterone and cortisol were assayed by radioimmunoassay methods. The results obtained in this study are as follows. 1. The two-breed cross gilt was 9.1 days faster in age at puberal estrus, 1.4 heads larger in number of pigs born alive per litter and number of live pigs at 21 days, 2.9 ㎏ heavier in total litter weight at birth, and 14.3 ㎏ heavier in total litter weight at 21 days than the Landrace gilt. 2. The serum FSH concentrations from 15 days after mating to 10 days postpartum ranged from 1.35 to 1.80 mIU/㎖ in the Landrace and from 1.30 to 1.80 mIU/㎖ in the two-breed cross. But the significance was not recognized between the Landrace and the two-breed cross. 3. The LH concentrations ranged from 2.2.0 to 4.35 mIU/㎖ in the Lardrace and from 2.45 to 3.75 mIU/㎖ in the two-breed cross. But we did not find any differences between the Landrace and the two-breed cross. 4. The prolactin concentrations between the Landrace and the two-breed cross did not find any differences but they showed significant fluctuation during pregnancy. 5. In the Landrace and the two-breed cross, the estradiol-1.7β concentrations increased from 27.20 pg/㎖ and 27.56 pg/㎖ at 15 days after mating to 620.15 pg/㎖ and 652.80 pg/㎖ at the time of parturition, respectively. 6. The progesterone concentrations in the Landrace were higher than those in the two-breed cross from 15 to 30 days after matings, and vice versa from 75 to 105 days after mating. The concentrations in the Landrace decreased from 38.90 ng/㎖ at 15 days after mating to 16.85 ng/㎖ at 105 days after mating and rapidly declined at the time of parturition until the levels (1.35 ng/㎖) were reached. The concentrations in the two-breed cross ranged from 24.0 ng/㎖ to 21.1 ng/㎖ and then rapidly dropped at the time of parturition. 7. The cortisol concentrations (from 34.5 to 50.0 ng/㎖) in the two-breed cross were significantly higher than those (from 13.0 to 24.5 ng/㎖) in the Landrace throughout the pregnancy.