We assessed general practitioners' knowledge about the at-risk status of offspring of persons suffering from Huntington's chorea. Of 97 practitioners who were questioned about only one at-risk individual, 16 were aware of the person's at-risk status, while nine of 26 practitioners who were questioned about more than one at-risk person were aware of it. The results indicate that prophylactic action can be achieved more efficiently by registration of families in which Huntington's chorea occurs, followed by genetic counselling.