In the 20th century, large families – defined as the biological parenthood of three or more children – increasingly became the exception and have been further declining in numbers in recent years. Which findings exist on the distribution of large families among different parts of society? What is known about the determinants and mechanisms that increase (or decrease) the probability that parents will bear many children? The paper focuses on these questions and gives an overview of current research on the topic. The authors emphasize sociodemographic determinants of large families, such as education, employment, income and living arrangements. Furthermore, the family of origin and the number of siblings typically acts as a model for when the individual starts his or her own family. A main factor for a large family is a relatively short time span between finding a partner and the birth of the first and the second child. The paper also examines research gaps, for example the question of which characteristics of large families can be seen as the causes, and which can be seen as the consequences of a large family. The paper also points out that there is an insufficient distinction between large families as outlined here and large families in the sense of a household containing many children (which are not necessarily one's own).