To synchronize the estrus of buffalo heifers (n = 50),a luteolytic dose of a PGF2 analogue (15 mg luprostiol;Prosolvin®) was administered intramuscularly at a randomstage of the estrous cycle. The day of estrous expression following the first PGF2 dose was recorded and all heifersreceived a second intramuscular dose of PGF2(15 mg luprostiol) either in the early (6–9 days after estrus; n = 33)or late (11–14 days after estrus; n = 17) luteal phase.