This study aimed to evaluate the effects of some medicaments used (p.p.) on the reproductive parameters in cattle and buffaloes. postpartum These medicaments included GnRH (Buserelin = Receptal "Hoechst Veterinär" and Gonadorelin = Fertagyl "Intervet International"), GnRH (Cloprostenol = stimulant (Theriogon “ADWIA Egypt"), PGF2 Tierarzneimittle" and Dinoprost = Lutalyse Estrumate "Coopers "Upjohn - Belgium") and oxytocin “Chemical works of Gedeon Richter 311 Assiut Vet. Med. J. Vol. 42 No. 83, October 1999 LTD". The study was divided into 3 trials: First trial was carried out on 135 buffaloes. They were divided into 2 groups A and B. Group A (80 buffaloes) calved normally and the puerperium passed without any complications while group B (55 buffaloes) had abnormal parturition (dystocia), infected puerperium and/or retained placenta. Group B was treated by 4 terramycine tablets intrauterine and 40 ml terramycin L.A. i.m. Both A and B groups were divided into 4 subgroups. Subgroup A1 (20 buffaloes) and B1 (15 buffaloes) were injected at day 14 p.p. by 5 ml Receptal im. Subgroup A2 (20 buffaloes) and B2 (15 buffaloes) were injected at day 14 p.p. by 5 ml Fertagyl i.m. Subgroup A3 (20 buffaloes) and B3 (15 buffaloes) were injected at day 14 p.p. by 5 ml Receptal i.m. followed by 3 ml estrumate i.m. 9 days later (day 23 p.p.). Subgroup A4 (20 buffaloes) and B4 (10 buffaloes) were used as control and injected by 5 ml saline i.m. at day 14 p.p. The results of the first trial revealed improvement in the reproductive parameters of these animals. Second trial was carried out 180 Holstein-Friesian cows. They were divided into 2 groups C (100 cows) and D (80 cows). Group C was injected directly after calving by 50 i.u. oxytocin and divided into 4 subgroups. While group D did not receive any treatment after calving and divided into 3 subgroups. At day 14 p.p., subgroups C1 (30 cows) and D1 (30 cows) were injected i.m. by 5 ml Receptal, subgroups C2 (30 cows) and D2 (30 Cows) were injected i.m. by 5 ml Fertagyl, subgroup C3 (20 cows) was treated orally by lgm/10 kg B.W. Theriogon, while subgroups C4 (20 cows) and D3 (20 cows) were used as control and injected i.m. by 5 ml saline. The results indicated that, injection of oxytocin directly after calving in C subgroups followed by GnRH either Receptal, Fertagyl or GnRH stimulant (Theriogon) at day 14 p.p. improved the reproductive parameters in these animals. Third trial was carried out on 100 Holstein Friesian cows. They were injected at day 14p.p. by 5ml Receptal i.m.. At day 42 p.p., all cows were injected i.m. by 5 ml lutalyse (first injection), 40 cows came in estrus followed injection and only 15 cows from them became pregnant with 37.5% conception rate and 2.7 services per conception. Cows that did not come in heat after first lutalyse injection (60 cows) were injected 14 days later by second lutalyse injection (day 56 p.p.), 50 cows (83.3%) came in heat and only 35 cows (70%) became pregnant while services per conception was 1.4. After 1" and 2 lutalyse injections, 90 cows came in heat from them 50 became pregnant with conception rate of 55.6% and services per conception were 1.8. Cows did not come in estrus after 21 lutalyse injection (10 cows) and those non pregnant 40 cows were injected by 2 doses of lutalyse injection 11 days interval, 35 of them came into heat and later on 27 from them became pregnant with conception rate of 77.1% and services per conception were 1.3. Total results of 3"" trial were 90.5% conception rate, 1.6 services per conception and 96.5+5.5 days open. Finally, it could be concluded that, treatment of buffalo cows with GnRH at day 14 p.p. followed by PGF2 at 9 days later (day 23 p.p.) improved the reproductive efficiency of buffalo cows. While 2nd trial indicated that, injection of Holstein Friesian cows directly after calving by oxytocin followed by GnRH (Receptal or Fertagyl) injection at day 14 p.p. will improve the reproductive parameters in Holstein Friesian cows. Also, injection of Holstein Friesian cows at day 14 p.p. by Receptal followed by PGF2 at day 42 and 56 p.p. improved the reproductive parameters in that cows.