As many as 4.75 milliongazelle may have occurred in Mongolia as recently as80 years ago (Milner-Gulland and Lkhagvasuren, 1998).Population assessments in 1978 and 1979 estimatedthe total population to consist of 250,000-270,000 and250,000 individuals respectively (Tsagaan, 1980; Sokolovand Lushchekina, 1997). Epizootic disease and extremedroughts in 1980 reduced the population to approximately150,000-180,000 individuals, but by 1981, the number ofMongolian gazelles had increased and stabilised at around300,000-400,000 individuals (Lushchekina et al., 1983).In 2002, a nationwide population assessment estimated the population to consist of 800,000-900,000 individuals (Olson et al., 2005). The population may have fl uctuated between125180,000 (Lushchekina, 1990) and 2.67 million individuals (results from an unpublished aerialsurvey with a standard error of 472,000) over the past 20 years. Population estimates varywidely due to differences in survey methodology and intensity, and as a result of populationfl uctuations casued by natural mortality and disease, therefore population estimates should betreated with caution (Milner-Gulland and Lkhagvasuren, 1998). Further surveys are requiredto clarify current population size. However, by 2000 it was known that this species occursin less than a quarter of its mid-twentieth century range (Lkhagvasuren et al., 2001). TheMongolian population is believed to be declining primarily due to exploitation, habitat lossand fragmentation, habitat degradation, competition for resources and human disturbance.Generation length has been estimated at fi ve years based on generation lengths of similarspecies. This species qualifi es as Endangered under Criterion A4cde as it is estimated thatthe causes of decline will result in a greater than 50% decline between 1996 and 2011.The assessment remains unchanged following application of regional criteria as there is nosignifi cant immigration from adjacent countries.