Serum progesterone concentrations of pregnant and non-pregnant Hanwoo were compared to evaluate the possibility of early pregnancy prediction. Twenty five female Hanwoo were devided into two groups. Eighteen heads were injected with 980$mu extrm{g}$ tiaprost trometamol salt(Iliren:PGF2$alpha$ analogue) for estrous synchronization and fifteen heads of them were inseminated artifically and seven heads were non-treated. Blood samples were collected from the jugular vein before PGF2$alpha$ injection and on day 0, 18, 21 after estrous induction. Pregnancy of cattle was confirmed by rectal palpaton after 60 days of artificial insemination. The serum progesterone concentrations at heat showed no significant differences between pregnant and non-pregnant while on day 18 and 21 after estrous induction showed significant differences(p<0.05). The accuracy of pregnancy diagnosis on day 18 and 21 after estrous induction was 85.7 and 71.4% respectively while that of non-pregnancy were 71.4 and 100.0% respectively.