Ultrasonographic diagnosis of genital disease and early pregnancy diagnosis was performed in Korean native cattle. The size of ovarian follicle in preovulation, luteal stage and follicular cyst was 18.9, 9.2 and 27.6 mm, respectively, and the thickness of follicular wall was 2.3, 1.8 and 2.8 mm, respectively. The size of corpus luteums in formation stage, activity stage, regression stage, cystic corpora lutea and luteal cyst was 6.2, 11.3, 8.6, 26.7 and 25.9 mm, respectively. The thickness of luteal wall in cystic corpora lutea and luteal cyst was 8.4 and 4.9 mm, respectively. The size of embryo or fetus on day 25, 27, 30, 35, 40, 45 and 50 was 0.8, 0.9, 1.3, 1.5, 2.2, 2.8 and 3.8 cm, respectively. The size of amniotic vesicle on day 25, 27 and 30 was 1.2, 2.1 and 3,0 cm, respectively. The diameter of pregnant uterus on day 25 and 27 was 7.0 and 7.8 cm, respectively. It was concluded that the ultrasonographci values determined in this study can be used as references for the treatment of genital disease and early pregnancy diagnosis in Korean native cattle.