Preventable adverse drug events (ADEs) are a source of avoidable hospitalizations, morbidity and mortality, especially among those older than 65 years. Computerized decision support systems (CDSSs) can identify and address ADEs, but relatively little has been written about the effectiveness of such system in the community setting. This article will review some important studies on the causes of medication-related admissions in the ambulatory setting, where a lack of communication among prescribers creates a virtual minefield of medication risk. Some preliminary data will show how the application of CDSSs can affect the outcomes of care, including a reduction in preventable admissions and readmissions.