Huntington 's chorea is one of the major inherited diseases. I t is a chronic, incurable condition resulting in progressive mental and physical deterioration, usually characterised by a combination of involuntary movements and loss of intellectual faculties such as memory and concentration. Onset is usually in middle life. The gene can be t ransmit ted through either parent, and both sexes are equally affected. The sufferer who carries this gene has a 50-50 chance of passing it on to his or her children, and, as far as we know, it never skips a generation. Thus, children with an affected parent have a 50-50 chance of developing the condition themselves, and, if they do, of passing it on to their children. Truly, it can be said that, they live with a hidden disability. There is no predictive test, so they cannot know whether or not they themselves carry the gene until they reach late middle age at least {unless, of course, they develop symptoms earlier}. Even if they do not develop the complaint, they probably have had to live for many years with the worry that they could develop it, a worry that they often find very difficult to share with anyone else, even members of the same family. Children at risk of developing Hunt ington 's chorea can face a series of agonizing decisions with regard to marrying and bearing children themselves. First, do they tell their fiance or spouse? This can be particularly difficult where the parent at risk may not yet show signs of the complaint, but has still not lived through the high-risk period; or where the parent has vague symptoms which could be the beginning sign of H.C., but equally could be attributable to other causes. Secondly, do they have children or not? If they want children but are very worried about the possibility of passing on the complaint do they wait until the diagnosis is confirmed or otherwise in the parent?