Many who would like to improve patient safety in health care have advocated for the widespread adoption of computerized physician order entry and electronic medical records. However, unforeseen consequences of this new technology may put patients at greater risk of harm, not less. The authors present a clinical scenario that demonstrates system vulnerabilities in the interface between humans and such technology. Furthermore, the authors suggest that managers could anticipate these vulnerabilities by using techniques such as cause-and-effect analysis or failure mode and effect analysis, both before the installation of electronic medical records and as ongoing surveillance mechanisms. The case study demonstrates that adoption of technology is not a quick fix to the patient safety issue; proactive and ongoing efforts to address the human factors issues raised by the introduction of new technology will be required to prevent patient harm.