An investigation on the efficacy of Ov-synch and modified Ov-synch with single dose of PGF2 Alpha in combination with GnRH in Synchronization of estrus in HF x local cross bred cows was conducted in and around Mekelle, From November 2009 to May 2010. A total of 20 animals, non cyclic (presence of well developed CL in either ovary) were inducted in to the experiment. Based on clinical examination animals were divided in to two groups. Group I animals: in clued both types of cycling with a CL and non cycling with out CL and received an IM dose of 75micro gram GnRH on day 0, 25mg PGF2 Alpha on day 7 followed by a second dose of 75microgram GnRH on day 9, all the animals were given a single insemination 24hrs after the second GnRH administration. Group II animals: were all cycling animals with a well developed CL in either ovary, received a simultaneous administration of 25mg PGF2Alpha IM and 100mg GnRH IM and give two fixed time insemination at 48 and 72 hrs after the treatment Five animals were excluded from the study due to various reasons.