Double-blind, Placebo-controlled Study of Oral Dimebon in Subjects With Mild to Moderate Alzheimer's Disease

Inclusion Criteria:

1. Males or females greater than or equal to 50 years of age.

2. Diagnosis of Alzheimer's Disease according to Diagnostic and Statistical Manual ofMental Disorders, Fourth Edition, Text Revision (DSM-IV TR) and Mini Mental State Exambetween 10 and 24, inclusive and Modified Hachinski Ischemia Score less than or equalto 4.

3. Brain imaging such as MRI and/or CT within one year of enrollment.

4. Subjects must have a guardian or caregiver who assists the subject at least 5 days perweek (at least 3 hours/day).

5. Subjects must be able to cooperate with drug administration (including the ability toingest oral medications) and study procedures and abide by study restrictions.

6. Subjects must have at least 6 years of prior education and should have previously (inpre-Alzheimer's condition) been capable of reading, writing and communicatingeffectively with others.

7. Subjects must be willing and able to give informed consent or have a mentallycompetent legal representative authorized to provide informed consent on their behalf.

8. Residence in an assisted care facility is allowed if subject is living independently.

Exclusion Criteria:

1. Major structural brain disease

2. Major medical illness or unstable medical condition within 6 months of screening thatmay interfere with the subject's ability to comply with study procedures and abide bystudy restrictions.

3. Residence in a nursing home or assisted care facility that provides the subject with 24-hour care and supervision.

4. Women who are pregnant, nursing, or if of child-bearing potential not using amedically accepted, highly effective method of birth control.

5. Active alcohol dependence or drug abuse.

6. Use of the following medications within 60 days prior to enrollment:cognitionenhancing agents, narcotic analgesics, low potency neuroleptics, antihypertensiveagents with frequent Central Nervous System (CNS) side effects, anti-Parkinsonianmedications, medications with central anticholinergic activity, medications forepilepsy, lithium.

7. Participation in an investigational drug or device study within 30 days prior to studyentry, or 60 days prior to study entry if the investigational drug study involvedtherapy for Alzheimer's Disease.