Abstract: The present study was designed to investigate the effects of administration of prostaglandin F2 (PGF2 ) during postpartum on uterine involution, length of postpartum period, days open and the number of services per conception in cross-bred Sudanese dairy cows. A total of 35 cross-bred dairy cows were employed to execute the effect of PGF2 on the above mentioned postpartum parameters. The cows were randomly distributed into 3 groups A, B (15 cows each) and C (5 cows). Group A is further subgrouped into 3 subgroups (5 cows each). The first subgroup was intramuscularly injected with 500 ?g of PGF2 on day 7, the second subgroup was injected on day 14 and the third subgroup was injected on day 21 postpartum. Group B was subgrouped into 3 subgroups (5 cows each). The first subgroup was given a double injection of PGF2 (500 ?g) on days 0 and 7, the second subgroup on days 8 and 14 and the third subgroup on days 15 and 21 post partum. Group C was employed as untreated control. The results of this experiment showed that in both treatment groups injection of PGF2 similarly reduced (P< 0.05) the time taken for uterine involution as compared with the control. Moreover, the lengths of the postpartum period and the days open were significantly reduced (p<0.001, p<0.01, respectively). However, single injection of PGF2 during the first week has no effect (p>0.05) on the postpartum period and the days open. Also the results showed that in either treatment groups administration of PGF2 during the second or the third week similarly reduced (p<0.05) the number of services per conception, but treatment during the first week has no effect (p>0.05). It is concluded that the use of PGF2 during early postpartum improves the reproductive efficiency of cross-bred dairy cows.