AdvancePCS is America's leading pharmacy benefit services organization, serving more than 75 million health plan members, managing 550 million claims annually, and managing more than $28 billion in prescription drug spending on behalf of its health plan sponsors on an annualized basis. Advance Paradigm and PCS Health Systems combined to form AdvancePCS, which offers the most extensive array of healthcare resources available from any single source. AdvancePCS also provides health improvement programs, clinical research, data integration and analysis, mail service, specialty pharmacy, disease management and online pharmacies, healthcare discount programs for uninsured and underinsured consumers, and a leading eHealth portal on the Web. Caremark Rx completed its merger agreement with AdvancePCS in 2004, resulting in one of the two largest pharmacy benefit managers in the nation.