Adverse drug events (ADEs) are widely recognized as the most common type of iatrogenic injury occurring in hospitalized patients. Recent statistics released by the Agency for Healthcare Quality and Research indicate that over 770,000 people are injured or die in hospitals each year from ADEs (Reducing, 2001). Not only do ADEs pose a significant threat to patient safety, they are costly. Patients who experience ADEs are hospitalized an average of 8 to 12 days longer than patients who do not suffer ADEs, resulting in an estimated annual cost of between $1.56 and $5.6 billion. In a study by Leape, Bates, Cullen, et al. (1995), it was concluded that 78 percent of errors leading to ADEs are due to inadequate information management systems. Computerized provider order entry (CPOE) systems are a type of information system that can significantly improve medication safety and decrease ADEs. Limited research attention, however, has focused on factors that contribute to successful CPOE system implementation and the impact that these systems have on ADE incidence, especially in non-teaching community hospitals. A three-year study is proposed to coincide with the implementation of a commercial CPOE system in three non-teaching community hospitals in an integrated health care delivery system in Southern California. The specific aims of the longitudinal study are to 1) test a theoretical model positing relationships between CPOE system implementation variables (i.e., information technology/systems (IT/S) innovation readiness, perceived usefulness, and satisfaction), and ADE incidence; 2) test the effect of a commercial CPOE system on ADE incidence; and 3) explore the impact of hospital contextual factors on CPOE system implementation variables and ADE incidence. A descriptive design with correlational, comparative, and exploratory components will be used to address study aims. Surveys of CPOE system users will be done to collect IT/S innovation readiness, perceived usefulness, and satisfaction data. ADE incidence will be collected using procedures adapted from those developed by the AIDE prevention study group at Brigham and Women's Hospital. Data will be analyzed using statistical techniques consistent with design approaches.