The present study was carried out on 342 imported Friesian cattle to investigate the problem of placental retention with emphasis on some reproductive performance and blood constituents. Blood samples were collected from cows which retained their foetal membranes for more than 24 hours after birth as well as normal parturient cows. Results indicated that retained placenta occurred in 16.72 % of cases, predominate in primipara (34.10 %) and during the hot season of the year (55.55 %). Significant decrease in plasma magnesium (P < 0.01); Inorg. phosphorus and Iron levels (P < 0.05) and increase in plasma progesterone values were detected in cases with retained placenta as compared to normal parturient cows. Moreover, the retained placenta causes delayed first post partum heat, calving interval with a reduction in fertility and decrease in milk yields.