Alzheimer's disease is one of several brain disorders under the broad category of dementia. It is a gradually debilitating illness with no known cure. The first symptom is usually a slowly increasing memory loss, beginning between 40 and 65 years of age. As the disease progresses, the brain begins to deteriorate more rapidly, until it literally stops functioning. Of great concern is the projection that the number of people who will have Alzheimer's disease will double by the year 2030 because of the rising elderly population. Treating this population will escalate from the current estimate in excess of $2.5 billion to more than $6 billion. Speculation toward the increasing costs in money and workforce has led to an accelerated program in search of a cure or at least a symptomatic therapy for this condition. One of the most promising research leads is the striking connection between Alzheimer's disease and Down's syndrome and certain cancers: --Virtually 100% of patients with Down's syndrome who survive past age 35 show the same mental deterioration and identical brain changes seen in patients with Alzheimer's disease, including the presence of plaque and neurofibrillary tangles.--The presence of a high percentage of Down's syndrome among relatives of patients with Alzheimer's disease. --A high incidence of certain types of syndrome and among relatives of people who have Alzheimer's disease, such as leukemia, lymphomas, Hodgkin's disease, and immune system disorders. The key to the intercorrections between Alzheimer's disease and Down's syndrome seems to be a genetic component related to chromosome 21.(ABSTRACT TRUNCATED AT 250 WORDS)