An alert system triggered by 37 drug-specific adverse events was programmed into a 650-bed hospital information system. The investigators found that 53% of the alerts were valid ("true positives") and that 44% of these had been unrecognized by the prescribing physicians prior to notification. The authors conclude that computer alert systems can help prevent a wide range of adverse drug events. This study was one of the first to support the use of trigger systems to recognize and help prevent medication errors.