Various forms of family organization among Russian peasants and urban dwellers coexisted from the sixteenth to the beginning of the twentieth centuries. The correlation of family types changed and was a function of circumstances and economic conditions. The available data indicate that from the middle of the sixteenth century to the middle of the nineteenth century, extended and multiple families predominated among peasants, though the relationship between single-family and multifamily households changed. In the second half of the nineteenth century, a steady process of nuclearization of family structure began, as a result of which the simple family gradually replaced multiple families at first in the cities later in the villages.