We review the extent and functionality of computerized physician order entry (CPOE) systems in seven Western countries. We compare nations’ implementation levels; linkages with other health care information technologies; amount and types of use by clinicians; drivers of implementation; inclusion of decision-support systems and electronic medical records; and goals (for example, patient safety and efficiency). Implementation of CPOE is slower and more problematic than anticipated (adoption rates are 20 percent or less) and often poorly integrated, inducing new errors and generating frustration with user interfaces and repetitive tasks. Nevertheless, the advantages of CPOE remain compelling.