This is the first publication of the presence of Huntington's disease (HD) in Colombia. We studied four families comprising nine adult HD patients and 45 high risk adult offspring; all received complete physical, neurological and neuropsychological examinations. Among affected individuals, intensity of mental involvement varied in direct proportion with duration of the symptoms. The HD patients and some of the asymptomatic offspring displayed similar low scores on standardized tests of memory, language and constructive abilities. Prolonged follow-up of the latter group will allow assessment of the potential value of such tests for early diagnosis. The sequence followed by mental deterioration is discussed.