The present work was conducted to evaluate the efficacy of two superovulatory regimens to determine the diameter of follicle using ultasonography to monitoring the ovarian activity for superovulation in 21 buffalo cows, giving PMSG and PGF2α. Superovulation regime was done by injection PMSG (3000 IU) when follicular diameter of the dominant follicles reach 5-7 mm (G1, n=7), >7-9 mm (G2, n=7,) and >9 mm (G3, n=7). Buffaloes in all groups were injected with 2 ml PGF2α and naturally inseminated depend on detection of estrous within 48-72 h of PGF2 injection. Flushing was conducted 7 days after insemination to determine the ovulatory response. Ultrasonography device was used during treatment period to record the number of follicles and CL and diameter of the follicles for PMSG injection. Results showed that the duration from Day 0 (estrus) up to PMSG injection was earlier (P<0.05) in G1 than in G2 and G3 (day 7.04 vs. days 9.2 and 9.8, respectively), but did not differ significantly in G2 and G3. The observed insignificant early time of treatment in G3 than in G2 was associated with wider range of treatment time in G3 than in G2 (day 8-10 vs. day 8-12). All buffalo cows in all groups came in estrus showing an estrus rate of 100% in each group. All buffaloes in G2 (100%) produced CL vs. 71.4 and 85.7% of buffaloes in G1 and G3, respectively. No embryos were produced from animals in G1, although 71.4% of animals in this group produced ovulation sites. Response rate of embryo production doubled in G2 as compared to G3 (57.1 vs. 28.6%). Buffalo cows in G2 showed insignificantly the highest total ovulatory response as compared to G1 and G3 (2.71 vs. 2.14 and 2.29, respectively). Number of unovulated follicles was insignificantly lower, while number of CLs per animal (total or responded animals) was higher (P<0.05) in G2 than in G1 and G3.Animals in G2 showed the highest (P<0.05) average number of CLs per responded animal, while number of embryos per responded animals or animals produced embryos was insignificantly the highest in G2 as compared to other groups. Buffalo cows in G2 produced embryos at morula (2 embryos/group) and blastocyst (2 embryos/group) stages, while those in G3 yielded embryos only at compact morula (2 embryos /group) stage. In comparing embryo production of G2 and G3, results revealed that averages number of total and transferable embryos were greater in G2 by about 50% than in G3. These findings are associated with higher recovery rate of total embryos in G2 than in G3, respectively. The obtained results indicated that the potentiality of PMSG injection to induce high superovulatory response in buffaloes is highly related to follicular diameter. Under the experimental conditions of the present study, appropriate time for superovulation in buffalo cows treated with 3000 IU of PMSG was when diameter of the dominant follicle reached a rang between ≤7 and 9 mm to reflect the highest ovulatory response.