The necessity of constructing a measure of ethnic homogeneity of the population of the different countries is founded. The advantages and shortcomings of different indices used for this purpose are discussed. The indicators according to which the different ethnic communities and groups are con-verging (respectively diverging) are also discussed. It is established that the language and territorial proximity are most important. Their definition does not cause special difficulties. For other types of proximity - religious, racial, economic, etc., considerable difficulties arise for their measurement. A coefficient of population ethnic homogeneity is proposed. It accounts for the number of the respective ethnic group and the degree of proximity to the basic (the most numerous) ethnic group in the country. For the definition of this proximity a range scale is applied. A classification of the coefficient of ethnic homogeneity is done. Examples for calculating the coefficient for different countries are given.