OBJECTIVES To quantify medication wastage for Lipid Lowering Agents, Antihypertensive Therapy, and Proton Pump Inhibitors. METHODS This study focused on drug waste for new to therapy patients. The therapy classes under consideration were Lipid Lowering Agents (N=12,978), Antihypertensive Therapy (N=15,975), and Proton Pump Inhibitors (N=14,365). The claims came from an aggregate of a segment of Medco Health Solutions clients. We calculated overall percentage of patients that wasted medication as well as percentage of days supply that they wasted. To focus on avoidable waste, we defined a wastage event as a switch within therapeutic class. We also stratified the days supply into 3 categories less than or equal to 30 days, between 30 and 90 days, and greater than or equal to 90 days. RESULTS For Lipid Lowering Therapy: Overall 1.5% of patients had wastage of 0.7% days supplied. Stratification by days: days