An ecological study of Swayne's haltebeest (Alcelaphlls bliselaplllls SlVaYllei), an endangeredrnsubspecies of antelope, was made fium February 1999 to December 1999 in Senkele Swayne'srnhaltebeest Sanctuary (SSHS) located 300 km from Addis Ababa. Data regarding population size,rnstmcture, vegetation community utilization, home range and daily activities that included both dryrnand wet seasons were gathered. A direct count method was employed in estimating the populationrnof the hartebeest in about 28 km2 of its natural habitat.rnThe total estimate of Swayne's hartebeest was between 145 in the wet season and 179 in the dryrnseason. Classification of 142 animals in dry season and 123 animals in wet season indicatedrndifferent sex and/or age stmctures for the population. The majority of the population was largelyrncomprised adult and sub-adult females (52.2%) adult and sub-adult males (31.6%). The proportionrnof the young constituted (16.1 %).rnHerd size altered monthly. A stable sub-group unit composed of 12 animals was observed. Thernmaximum group size observed was 45. Hartebeest's number of groups were largest in wet seasonrnin the open plain and smallest in dry season in woody cover.rnThe results of the study showed that Swayne's llaltebeest occupied the 3 vegetation communities inrnthe Sanctuary. Their distribution and vegetation community utilization is found to be influenced byrnfood availability and the presence of human and domestic animals within the Sanctuary. Thernanimals were observed utilizing the 3 vegetation communities in both seasons, howev;r, there wasmore utilization of the Pennisetul1l Grassland (PG) community (77.2%) in the wet season andrn62.5% in the dry season.rnLocating all groups during counting provided the movement and home range data of both seasons.rnMinimum Convex Polygon (MCP) method was used to calculate the home range size. Seasonalrnhome range size varied. Wet season home range size was twice larger than that of the dry seasonrn(16 vs 9 Jan2).rnSwayne's hartebeest activity was recorded at 4 min-intervals for continuous period of 12 In' on twornconsecutive days every month of the eight months of the study period. About 48.9% of the totalrntime was spent in feeding and about 38.6% in resting (standing and lying). There were two feedingrnpeaks, one in the moming and another in the aftemoon, and one resting peak in the middle of thernday.