This research aimed to explore the influence of an economic opportunity and characteristics of herders on the composition of their livestock in Mongolia. In order to achieve our purpose we compared three suburban areas, Bornuur, Altanbulag and Argalant. Bornuur has the biggest opportunity of selling cow`s milk, followed by Altanbulag and Argalant.
    Socio-demographic attributes were obtained by interviewing 191 households. We adopted the negative binomial regression model incorporating the number of present or expected cattle as the response variable, the household’s attributes as the explanatory variables, each area as dummy variables and the number of present or expected total livestock as an offset.
　  The proportion of cattle among livestock in Bornuur was much larger than other two areas while there was no significant difference between Altanbulag and Argalant. In terms of future livestock flock, Altanbulag is expected to have more cattle than Argalant. We confirmed that elder herders are likely to have more cattle. Even though younger generations in Bornuur also plan to own more cattle than others.
    These results showed that the opportunity of selling milk would increase the number of cattle and change young herder`s idea of their livestock composition.