OBJECTIVE: To determine drug costs to establish and maintain treatment for hypertension with amlodipine and felodipine. METHODS: Data from published reports of 4 controlled trials directly comparing amlodipine and felodipine were analyzed. Three trials were identified from a comprehensive Medline search; one trial was cited as a reference. For one study, the unpublished study report supplemented information from the published report. In all 4 trials, subjects with mild-to-moderate hypertension were started on 5mg of study drug and titrated to higher dosages after 2 to 8 weeks if hypertension was not controlled. Maximum dosages of amlodipine and felodipine were 10mg in 3 studies. One study allowed titration to felodipine 20mg. In another study, lisinopril was added if hypertension was not controlled by monotherapy. Data were pooled across studies to determine the fraction of patients titrated to greater than 5mg or dual therapy. For the cost analysis, average drug costs to establish and maintain treatment were calculated from dosages during and at the end of each trial, respectively. Where published reports did not indicate timing of withdrawals, upper and lower limits yielded high and low estimates of cost to establish treatment. Average (US) wholesale prices were used for drug costs. Statistical significance was assessed with a chi-square test. RESULTS: Fewer amlodipine (45%) than felodipine (55%) patients were titrated to greater than 5mg or dual therapy (p=0.013). Average drug costs/patient-day across the four studies ranged: Amlodipine Felodipine Establish treatment $1.49-$1.59 $1.17-$1.71 Maintain treatment $1.63-$1.74 $1.28-$1.98 Varying assumptions about timing of withdrawals changed results by 3-percent or less. Higher costs with felodipine were found in the study that allowed titration to felodipine 20mg. CONCLUSION: The higher price of amlodipine may be offset by higher dosages or greater need for dual therapy with felodipine. Actual drug costs depend on dosages and combinations used in practice.