This report reviews clinical neuropsychiatric findings and opportunities for research in Huntington's, Wilson's, and Fahr's diseases. Consistent, systematic methodology is lacking among neuropsychiatric studies in these lenticulostriatal diseases. Systematic cross-sectional and longitudinal assessments are needed to ascertain the prevalence of psychiatric disorders as a function of disease course. Preliminary synthesis of existing data suggests the following heuristic relationships in these diseases: depression with parkinsonian states; personality changes with caudate or putamen disease; psychosis, impulsivity, and sexual disorders with caudate disease; dementia and mania with caudate and pallidal diseases; and compulsions with pallidal disease. Correlation of neuropsychiatric findings with disease stage, clinical signs, and radiologic, metabolic, physiologic, and pathologic markers of disease will add to our understanding of these conditions.