The eugenics movement, started in England in the 1860's, deals with the racial, inheritable qualities of a population. Given the current interest in the history of science, sociobiology, and issues such as the inheritability of intelligence, the family studies cannot be dismissed as ideological aberrations or sociological folklore. They raise fundamental questions about the relation between biology and society and the meaning of evolution. The family studies are based on the belief that social problems are biologically based and linked. They also assume that if a trait shows up in more than one generation, it is inherited; that personal defects are more important than social or environmental factors in causing social problems; and that the distribution of social power can be explained in terms of heredity. The family studies reflect ways in which thinking about heredity changed over the five decades during which they were produced. Those written before 1912 showed little interest in the processes by which degeneration was transmitted. After Mendel's laws of inheritance were rediscovered and applied to humans in the early 20th century, researchers became more interested in mechanisms of heredity. Overall, the family studies may contribute to current discussions of such issues as the alleged "birth dearth" of genetically healthy individuals and of the alleged role of biological factors in criminal behavior. References, tables, figures.