Tacrine is the first drug approved for the treatment of mild or moderate Alzheimer's disease (AD). The present study evaluates the potential ramifications of tacrine on AD costs. An economic model was specified to link cognitive changes observed in a 30-week clinical trial of tacrine with estimates of the cost of AD, drug therapy, monitoring, time in a nursing home, and survival from diagnosis. Two groups were evaluated: (1) 367 patients receiving varying doses of tacrine, including treatment failures, and (2) 67 patients able to tolerate the high dose of 160 mg/day. Based on a literature review, a patient with AD survives a mean 4.4 years from diagnosis and incurs lifetime treatment costs of $57,169 (1993 dollars). Patients taking doses of 80-160 mg/day, showed an improvement in Mini-Mental State Exam (MMSE) of 1.0 point, which resulted in 9.5 months of predicted community and institutional care avoided, for annual savings of $2,243/patient (range, $-109 to $3,342). Patients able to tolerate the 160-mg dose improved 2.0 points on the MMSE, resulting in a prediction of 12.1 months of reduced community and nursing home care, for annual savings of $4,052/patient. Tacrine therapy could generate savings up to 17% of the current costs of AD, or a total of $3.6 billion annually for the estimated 1.6 million persons with mild-to-moderate AD.