While computerized physician order entry (CPOE) is expected to significantly reduce medication errors, systems must be implemented thoughtfully to avoid facilitating certain types of errors. This AHRQ-funded study identified 22 situations in which the CPOE system increased the probability of medication errors. According to the study, these situations fell into two categories: information errors generated by fragmentation of data and hospitals' many information systems, and interface problems where the computer's requirements are different than the way clinical work is organized. The study looked at clinicians' experience in using one CPOE system at a major urban teaching hospital.