This study analyzed more than 1500 adverse drug events and discovered that nearly 28% were preventable. Investigators studied a large population of Medicare enrollees in a single multispecialty group practice capturing events through a number of strategies that included reports from health care providers, review of hospital discharge summaries and emergency department notes, free-text review of electronic clinic notes, and others. The overall rate of adverse drug events approached 50 per 1000 person-years with the most serious events and preventable events occurring at the time of prescribing and monitoring. The authors present a detailed classification of the drug events along with the most common events and medications implicated. While this study focused on an elderly population, a similar study presented their findings from the ambulatory setting in general.