Mongolia's population is sparsely distributed, young, and increasing rapidly. With an around midyear 1989 population of 2,125,463, the average population density was 1.36 people per square kilometer. The annual growth rate was about 2.7 %, which, if sustained, would double the population in 27 years. The rate of natural increase was the result of high birthrates and of death rates that were comparatively low by world standards. Mongolia does not publish figures for infant mortality, but estimates in the late 1980s ranged between 49 and 53 per 1,000 birth. The population's sex ratio was nearly even, with official 1986 figures showing 50.1 % of the total population as male and 49.9 % as female.

At the time of the founding of the modern state, the social composition was strongly determined by the then-prevailing religious traditions of the lamas (monks), who followed tenets derived from Tibetan Buddhism, with a strong admixture of more primitive elements. Control lay in the hands of the head of the Mongolian Tibetan Buddhist Church -who was proclaimed the khan of all Mongolia together with various local khans, hundreds of princes and noblemen, and the higher clergy. The new regime sought to replace feudal and religious structures with socialist and secular forms. During the 1930s the government closed monasteries, confiscated their farm animal and landholdings, induced large numbers of monks to renounce religious life, and eliminated others. The number of Buddhist monks dropped from 100,000 in 1924 to 110 in 1990. Many aspects of the national cultural traditions are preserved in museums.