A firm diagnosis of Huntington's Disease (HD) is based upon both clinical observation and a positive family history. 192 cases of HD occurred in South Wales over a 10 year period fitting both criteria but an additional 37 patients did not have affected relatives despite detailed enquiries. Twenty-two of these were still thought to have HD on clinical grounds whilst this diagnosis was thought less likely for 15. Definite post-mortem outcomes are known for 7 patients and the clinical diagnosis confirmed on 6 occasions. Details regarding these two groups are presented together with an additional case in which HD was given on the death certificate but a post-mortem revealed a diagnosis of Kufs' disease.