In this study, the effect of PGF:o + PGF^, GnRH + PGF,U, PRID + PGF3(! and ear implant + PGF:„ applications on estrus synchronization and fertility in cows in lield conditions were investigaled. A totaî ol 125 Holsteın cows were used as material. Cows were randomly divided in to five groups. Two injections of PGF:„ was applied 11 days apart in the first group (n=25). GnRH (day 0) and PGF:„ (7 day later) was injected in the second group (n=25). PRID's were inserted to the anterior vagina of each cow lor 12 days and PGFi„ was injected before the day of PRID removal in the third group (n=25). Ear implants were inserted to the ear of each cow subcutaneousty tor 9 days and PGF;„ was injected before the day of implant removal in the fourth group (n=25). Cows in the group V (n=25) were served as control. Artificial inseminations were performed twice at 72-96 hours m the group i and 48-72 hours in the groups II. til and IV after the last application. Cows in the control group (n=25) were inseminated with regard o the spontaneous estrous Pregnani cows were determined by rectal palpation between 60-90 days after the second inse ination. Estrous and pregnancy rates were °e100.0'o96 00, %100, %100 and %100; %84 00. %62.50, %84.00, %72.00 an ı %52.00. respectively, in the groups I, II, 111. IV and V identical estrous rates were found in all groups (P>0 05) Pregnancy rates in the groups I and III were higher than group V (P<0.05). However pregnancy rates were similar in the groups I. II. Ill and IV (P>0.05), In conclusion, it was determined that two injections of PGF2q. GnRH + PGF:a and implant +■ PGF?U methods are more economic than PRID + PGF,„ method Looking the more advantegeous about application easiness and agreement of fanner, the injections pf PGF V, 11 days apart and GnRH + PGF2u is more advantageous. However, it was concluded that, all of the synchronization methods used in our study were determined as useful because of allowing fixed-time insemination without estrous detection. synchronising estrous and increasing of pregnancy rates in field conditions.