The mouse has many advantages over human beings for the study of genetics, including the unique property that genetic manipulation can be routinely carried out in the mouse genome. Most importantly, mice and human beings share the same mammalian genes, have many similar biochemical pathways, and have the same diseases. In the minority of cases where these features do not apply, we can still often gain new insights into mouse and human biology. In addition to existing mouse models, several major programmes have been set up to generate new mouse models of disease. Alongside these efforts are new initiatives for the clinical, behavioural, and physiological testing of mice. Molecular genetics has had a major influence on our understanding of the causes of neurological disorders in human beings, and much of this has come from work in mice.