Dementia is an acquired syndrome of decline in memory and at least one other cognitive domain such as language, visuo-spatial, or executive function sufficient to interfere with social or occupational functioning in an alert person. Multiple diseases can cause the syndrome of dementia. The large majority of people with dementia have neurodegenerative disease or cerebrovascular ischemia as the underlying cause. Between 60% and 70% of people with the dementia syndrome have Alzheimer's disease; about 20% to 30% have vascular or mixed vascular and Alzheimer's disease causes. A smaller number have other causes such as Lewy body dementia, frontal dementia, Parkinson's disease, hypothyroidism, and vitamin B-12 deficiency. To date, research has produced no effective approach for primary prevention of dementia. Chemoprevention has been advocated, but data on effectiveness are lacking. Although control of hypertension reduces the risk of cerebrovascular accidents, its role in reducing small vessel vascular dementia is less clear. The wealth of literature has been on screening for dementia with the hope of reducing its burden of suffering by earlier intervention. Routine history and physical examinations do not readily diagnose dementia during clinic or physician visits. Multiple studies in the United States and abroad indicate low identification of dementia by primary care physicians. More than 50% of patients with dementia have never been diagnosed by a physician. This raises the possibility that effective screening tests might be able to identify people with dementia at an early stage, thus allowing the possibility of earlier intervention. Key question addressed include: KQ1: Does screening for dementia in older adults (over 60 years) do any of the following: improve or worsen patients. cognitive, social, or physical function? increase or decrease hospitalizations, institutionalizations, or health care visits? prevent or precipitate behavioral problems? alleviate or worsen caregivers. stress and coping? prevent or precipitate accidents, such as accidental falls or automobile crashes? improve or worsen patients. health-related quality of life? KQ2: What is the prevalence of undiagnosed dementia in primary care patients? What are the common causes of dementia in primary care patients? KQ3: Is there a reliable and valid screening test to detect dementia in primary care populations? KQ4: Do pharmacologic interventions of potentially reversible or irreversible dementia improve any of the 6 outcomes noted in KQ1? Such treatments include antiplatelet therapy for vascular dementia, cholinesterase inhibitors for Alzheimer's disease, thyroid treatment for hypothyroidism, and vitamin B-12 for vitamin B-12 deficiency. KQ5: Do nonpharmacologic interventions, such as sensory, environmental, behavioral, or activity-directed programs, improve any of the 6 outcomes noted in KQ1? KQ6: Do caregiver interventions improve any of the 6 outcomes noted in KQ1? KQ7: What are the adverse effects of screening for dementia? KQ8: What are the costs and cost-effectiveness of screening fordementia? KQ9: What are the adverse effects of dementia therapy?