When a new product is marketed, information obtained from strictly controlled clinical trials may not accurately predict its use within a managed care plan. Identifying the most cost-efficient therapy or service is of paramount concern. Although managed care plans can easily justify the formulary addition of a low cost per unit product, more difficulty arises when considering a higher-cost product. A retrospective analysis of pharmacy claims related to topical antifungal therapy for an HMO plan was conducted to determine the refill frequency and the total topical drug treatment cost for each of the antifungal agents researched. In this study, a manufacturer's claims of higher potency and shorter course of treatment could not be substantiated.