This article discusses the development of the statistical methods employed by psychiatrists to study heredity as a causative factor of mental diseases. It argues that psychiatric asylums and clinics were the first institutions in which human heredity became the object of systematic research. It also highlights the different concepts of heredity prevalent in the psychiatric community. The first of four parts traces how heredity became a central category of asylum statistics in the first half of the nineteenth century. The second (...) part deals with attempts to introduce new methods of surveying in order to generate more precise data about psychopathological inheritance in the 1860s and 1870s. The third part discusses how, by the end of the nineteenth century, a widespread discontent with the results of asylum statistics led to an increasing interest in the use of family studies. Finally, the fourth part examines the impact of Mendelian theory on psychiatric statistics in the early twentieth century. (shrink)