Ten adult female water buffalo were used in the present study (5 x [2n = 50] and 5 x [2n= 49] hybrids). Ovarian activity was monitored daily by transrectal ultrasonography between two consecutive ovulations. Observed follicular wave numbers were: 1 (n=1), 2 (n=4), and 3 (n=5). The interovulatory interval ranged 17 to 23 days. Differences in mean follicular diameter between follicles of the normal karyotype (2n=50) and buffalo hybrids (2n=49) were found on the second subordinate group of follicles (P<0.05) but not between dominant and third subordinates. Differences in circulating concentrations of P4 and estradiol were not statistically significant (P>0.05), whereas inhibin profiles were significantly higher in the hybrid group (P<0.05). Understanding the biological meaning of the difference in inhibin concentrations in B. bubalis female reproductive performance will require further investigation.