Tacrine, a centrally acting cholinesterase inhibitor, may improve cognitive and functional status in patients with mild to moderate Alzheimer's disease. In recent controlled trials, patients have shown improvement in cognitive assessment scores, but the clinical significance of such benefits remains unclear. Appropriate diagnostic evaluation is necessary to prevent inappropriate treatment in patients with non-Alzheimer's dementia. Hepatotoxicity and gastrointestinal symptoms are common adverse effects of tacrine, and frequent monitoring of liver function is required.