The principles of an anticoagulant-psychotherapy regimen for presenile dementia are discussed. Short histories are given of 10 patients (including one with Huntington's chorea as well as dementia) who responded well to this treatment. It is important to keep the blood prothrombin time at 2.0-2.5 times the control time. The earlier treatment is started, the better the result. Even in cases in which there is n o significant improvement, the prevention of further deterioration is of great value. If properly controlled, this regimen is relatively safe and can maintain or improve the quality of life for dementia patients. When brain deterioration is observed in patients past the age of 70, it is usually accepted as an unfortunate manifestation associated with the aging process. However, when observed in patients of the 40-60 age group, it is one of the most puzzling problems in medicine. Traditionally, age 6 5 is arbitrarily chosen as the dividing line for nomenclature: after that age the brain deterioration is called senile dementia; before that age it is called presenile dementia. It is our hypothesis that they both represent variations of cerebrovascular insufficiency, regardless of age. This paper concerns our recent experience with a therapeutic regimen developed during the past eleven years. Ten patients have responded favorably to this treatment in such a way as to refute the general belief that presenile dementia is an irreversible disorder with a steady downhill course.Nineteen years of general practice have afforded the writer ample opportunity for ob-