Semen was collected from six adult (3.5-7-year-old) Murrah buffalo bulls at weekly intervals for 1 year and evaluated for routine parameters, motion characteristics, reactivity in hypoosmotic solution, and acrosomal and other morphological abnormalities of the spermatozoa. The overall motility (MOT), straight line velocity (VSL), curvilinear velocity (VCL), linearity (LIN), lateral head displacement (ALH) and average path velocity (VAP) were 66.85+/-2.79%, 26.58+/-0.24 and 107.07+/-1.47 microm/s, 26.91+/-0.01%, 11.19+/-0.09 and 61.78+/-2.79 microm/s, respectively. Significant seasonal variation was observed in sperm kinematics and hypoosmotic swelling (HOS) reactivity. Except for LIN, the mean values of sperm dynamics were higher during summer and rainy season and significantly lower in winter season. Sperm kinematics showed significant (P<0.01) positive correlation (r=0.25-0.60) with plasmallemal integrity. Ejaculates with less than 50% HOS-reactive spermatozoa had significantly lowered MOT, VSL, VCL and VAP as compared to the ejaculates with >50% HOS-positive spermatozoa. No significant difference was observed in sperm kinematics among the ejaculates having 50-70% and >70% HOS-reactive spermatozoa. The trend of motion dynamics of the spermatozoa with respect to HOS reactivity was similar in all the three seasons (summer, rainy and winter). The results indicate that ejaculates having more than 50% of HOS-reactive sperm show a higher magnitude of sperm kinematics compared to ejaculates having less than 50% HOS-positive spermatozoa.