OBJECTIVES: Advantage90TM is Walgreens Health Initiatives' 90-day retail program allowing patients to obtain 90-day supplies of maintenance medications from a network of retail pharmacies. This study evaluated the changes in prescription drug utilization and costs after the introduction of this program. METHODS: Using a pre-post (8 months from the enrollment date) cohort study design, prescription records were obtained from Walgreens Health Initiatives' pharmacy claims database. Clients enrolled in Advantage90TM during January 1, 2004 and May 1, 2004 were included. Clients without 3-tier formulary design and rebate-eligibility were excluded. For the purpose of this study, specialty drugs were excluded. Number of prescription dispensed, costs per prescription (normalized to 90-day supply) and generic percentages in Advantage90TM, mail service and 30-day retail were analyzed and compared. RESULTS: Seventeen clients with a total of 236,950 eligible lives met the inclusion criteria. A total of 1,618,240 prescriptions, 802,345 in the pre period (5% mail and 95% 30-day retail) and 815,895 in the post period (14% Advantage90TM, 4% mail and 82% 30-day retail) were included. The average total cost per prescription was significantly lower in Advantage90TM than in mail service and 30-day retail ($129.39 vs. $191.15 vs. $205.09, p<0.0001). Health plans paid significantly less for per prescription in Advantage90TM than in mail service and 30-day retail ($100.08 vs. $159.48 vs. 155.01, p<0.0001). Per prescription co-payments from patients were $29.21 in Advantage90TM, $31.50 in mail service and $49.55 in 30-day retail. The generic utilization rate was higher in Advantage90TM than in mail service and 30-day retail (60.1% vs. 35.8% vs. 42.8%, p<0.0001). CONCLUSIONS: Availability of a 90-day retail program such as Advantage90TM can decrease total, health plan and member costs while increasing generic utilization rate. A 90-day retail program should be considered as an option to lowering prescription drug costs.