Probucol is a cholesterol-lowering drug that has been removed from the market in Canada and the US, but remains in clinical use in Asia. In rodents, probucol increases synthesis and availability of apolipoprotein E (apoE) in the cerebrospinal fluid (CSF). ApoE is the protein product of the polymorphic gene APOE, allelic variation in which remains the strongest known risk factor (other than age itself) for Alzheimer's dementia. Oral Probucol is absorbed variably. Administration of a single, fixed dose therefore results in a wide range of plasma concentrations when the drug is given to various individuals in a fixed dosage. Limited human data suggest that higher plasma and CSF concentrations of probucol result in stronger increases in CSF apoE concentration. The dual aims of DEPEND are therefore 1) to develop an individualized dosing regimen that will result in plasma concentrations that are likely to increase CSF apoE concentration by 50%; and 2) to treat 20 persons at elevated risk of Alzheimer's dementia, each at his/her ideal individual dosage, for 12 months, observing the resulting change in CSF concentrations of apoE. Simultaneously, subjects will be observed carefully for evidence of any treatment effects on cognition or other probable markers of progression in pre-clinical Alzheimer's disease, as well as safety risks that might deter further human experimentation with the drug.