The authors draw from their aggregated experience in qualitative assessment of clinical information systems in the United States, Europe, and Australia to propose a framework for understanding unexpected adverse consequences of patient care information systems (PCIS) on clinical work. The adverse effects are broadly divided into errors in the process of entering and retrieving information in or from the system and errors in the communication and coordination processes that the PCIS is intended to support. The authors highlight the mismatch between the linear, rigid design of software and the cognitive, social, and organizational realities of health care delivery. The article was among the first and most influential in a wave of papers highlighting potential drawbacks in clinical information technology, and tempering the impression of computerized provider order entry systems as a universal good.