This study found that after implementation of computerized provider order entry (CPOE) with robust decision support in two adult intensive care units, the rate of duplicate medication orders increased dramatically. Analysis by a physician and a human factors engineer identified several contributing causes. These ranged from limitations of the system itself (orders for electrolyte repletion were often entered immediately before and immediately after physician shift change, as the CPOE system did not reliably display completed orders) to changes in team workflow (prior to CPOE, only one member of the team would write medication orders on rounds, whereas with CPOE multiple team members could enter orders more or less simultaneously). Similar issues have been documented in prior studies of the unintended consequences of CPOE.