This study compared the use of two injections of prostaglandin F2α(PGF2α) given 11 d apart with the use of gonadotropin releasing hormone (GnRH) followed by PGF2α after 7 d for synchronizing estrus in beef heifers. Heifers synchronized with GnRH and PGF2α showed weak signs of estrus and were more difficult to inseminate. There were no significant differences in synchronization rate and pregnancy rate. Key words: Estrus synchronization, beef heifers, gonadotropin releasing hormone, prostaglandin F2α