Analysis of records of the marriages that were contracted in the city of Poltava revealed an increase in outbreeding between 1960 and 1985 in the Poltava population. This was expressed in increased ethnic diversity, proportion of interethnic marriages, migration range, and the parent-offspring and average marital distances, whereas the proportion of the indigenous ethnic group (Ukrainians) decreased. By 1995, outbreeding decreased: the ethnic composition of the population became more homogeneous (98% Slavic), the proportion of Ukrainians and the frequency of monoethnic marriages increased, and the migration range decreased. During the period studied, the population became more panmictic with respect to ethnicity and birthplace, with the social and professional subdivisions of the population remaining unchanged.