In light of the tremendous expansion in the number of selective serotonin reuptake inhibitors available to the clinician, the Pharmacy and Therapeutics Committee of the Denver Veterans Affairs Medical Center considered the advantages and disadvantages of fluoxethine, paroxetine, and sertraline, to determine which agent or agents would be carried on the formulary. The committed recommended sertraline as the preferred agent for the treatment of depression, panic disorders, and obsessive-compulsive disorders. The purpose of this retrospective study was to assess the economic outcome of that decision. The study population consisted of patients at the medical center who were receiving selective serotonin reuptake inhibitors during January through March of 1994 and those were receiving these agents between September 1995 and January 1996. The expanded collection period in 1995-96 was due to a relatively new medical center policy to offer 90-day fills on medication to reduce costs. The extended collection period assured a 100% sample of patients receiving these agents. The 1994 fluoxetine to sertraline dosage equivalency ratio was 20 mg:55.6 mg, based on average daily doses of fluoxetine and sertraline of 32.7 and 90.9 mg, respectively. The cost to the medical center for an average daily dose of fluoxetine was $1.86; sertraline cost $1.22 per day. The 1996 fluoxetine to sertraline dosage equivalency ratio (20 mg:51.3 mg) had not changed significantly since 1994, indicating that the dose of 20 mg of fluoxetine remained very close to a 50-mg dose of sertraline. The average daily doses of fluoxetine and sertraline (34.9 mg and 89.7 mg, respectively) were not significantly different than the 1994 doses. Only 33 patients had been prescribed paroxetine (average daily dose, 32.4 mg). On the basis of these values, the average daily cost of fluoxetine to the medical center was $2.01, compared with $1.18 for sertraline and $1.24 for paroxetine. This $0.83 per patient per day drug acquisition cost difference between fluoxetine and sertraline results in a drug cost reduction of $302,674 per year.