The present study aimed to determine the differences in semen parameters between Karan Fries (KF) and Sahiwal bulls and the correlation of hypo-osmotic swelling test with conventional semen parameters. A total of 24 ejaculates were collected from each breed and subsequently classifi ed according to their mass activity. The semen samples were further examined for progressive motility, sperm viability, sperm concentration and hypo-osmotic swelling test (HOST). The percentage of hypo-osmotically swelled spermatozoa was higher (P<0.01) in ejaculates of Sahiwal bulls than in KF bulls. However, the mass activity, percent progressive motility, viability and concentration of sperms did not differ (P>0.05) between the breeds. With respect to association between HOST and conventional semen parameters, HOST showed signifi cant (P<0.01) positive correlation with progressive motility (%), sperm viability (%) and sperm concentration in both breeds. This study indicated the HOST as an effective metho to test the fertility potential of semen samples for artifi cial insemination and zebu breeds ejaculates have more fertility potential as compared to crossbred ejaculates under heat stress.