The Institute of Medicine found that hospital-based emergency care was "at the breaking point" in a seminal 2006 report, in which emergency department (ED) overcrowding was identified as a major patient safety concern. Prior studies have also found that medication errors are a significant problem in the ED. This study sought to investigate the relationship between these two safety concerns. Detailed review of medication orders by pharmacists revealed a significant correlation between ED crowding and the frequency of medication errors. Overcrowding was one factor cited as a major barrier to implementing the National Patient Safety Goals for medication safety in the ED, and a medication error near miss in a busy ED is vividly illustrated in this AHRQ WebM&M commentary.