Bar coding technology is being rapidly adopted as a mechanism to prevent adverse events, including retained foreign objects and errors in blood transfusion. However, workarounds and unintended consequences of bar coding have also been reported. This study demonstrated that implementation of a bar-code–assisted medication administration (BCMA) system reduced medication errors in medical–surgical wards (after excluding time errors) but not in intensive care units. Findings showed not only improvements in patient identification practices but also an increase in nurse distractions during the administration process. The authors conclude that implementation of BCMA systems may have different effects in different patient care areas.