The objective of this study was to investigate the relationship between progesterone(P4) concentration, glucose, cholesterol, urea nitrogen and return of postpartum estrus for the purpose of improving reproductive performance in blood of Holstein dairy cows. Approximately seventy-five percent of the cows (128/170) had normal resumption of ovarian cyclicity (resumption within 40 days after calving), and 24.7% (42/170) had delayed resumption (did not occur until>40days after calving). Return of postpartum estrus was not significantly lower for cows with blood urea nitrogen (BUN) above 19 (mg/dl) than for cows with BUN below 19 (mg/dl). These results showed that the level of glucose, cholesterol and BUN affect the return of postpartum estrus. Considering the situation that estrous expression is decreased in recent years, effective nutrition management should be accompanied to improve reproductive performance.The objective of this study was to investigate the relationship between progesterone(P4) concentration, glucose, cholesterol, urea nitrogen and return of postpartum estrus for the purpose of improving reproductive performance in blood of Holstein dairy cows. Approximately seventy-five percent of the cows (128/170) had normal resumption of ovarian cyclicity (resumption within 40 days after calving), and 24.7% (42/170) had delayed resumption (did not occur until>40days after calving). Return of postpartum estrus was not significantly lower for cows with blood urea nitrogen (BUN) above 19 (mg/dl) than for cows with BUN below 19 (mg/dl). These results showed that the level of glucose, cholesterol and BUN affect the return of postpartum estrus. Considering the situation that estrous expression is decreased in recent years, effective nutrition management should be accompanied to improve reproductive performance.