In view of the substantial vegetation changes in Tsavo National Park and their possible effects on the herbivore fauna, this study was undertaken to obtain quantitative information on densities of several ungulate species and their biomass. Road strip counts (belt transects) constituted the main method used, supplemented by aerial counts in parts of the study area. Densities of most ungulate species are rather low, the maximum of 2–25 per km2 being attained by zebra in the southern poition of the study area. There are significant differences between two parts of the study area, related to differences in vegetation types. Mean biomass density is around 4000 kg/km2, of which ⅔-¾ is made up of elephants. Total biomass density compares well with that in areas of similar climatic conditions but is much lower than that in moist savannas of western Uganda and Zaire with higher rainfall.