This commentary on the article by Shulman et al. examines what we understand by 'medication errors', what we mean by 'computerized physician order entry (CPOE) systems', how we measure errors, and what types of errors we are 'reducing' with CPOE systems. As the research of Shulman and colleagues highlights, much of the existing research on CPOE systems does not differentiate among: types of medication errors; consequential versus inconsequential medication errors; CPOE systems that include/exclude formal decision support packages; and the extent to which decision support information is implicitly presented to physicians via the CPOE system, for example, pull down menus with dosages. I discuss these issues and their implications for the evaluation of CPOE systems and of other emerging healthcare technologies.