Summary: Objectives: To examine the impact of design aspects of computerized physician order entry (CPOE) systems for medication ordering on usability, physicians’ workflow and on medication orders. Methods: We systematically searched PubMed, EMBASE and Ovid MEDLINE for articles published from 1986 to 2007. We also evaluated reference lists of reviews and relevant articles captured by our search strategy, and the web-based inventory of evaluation studies in medical informatics 1982–2005. Data about design aspects were extracted from the relevant articles. Identified design aspects were categorized in groups derived from principles for computer screen and dialogue design and user guidance from the International Standard Organization, and if CPOE-specific, from the collected data. Results: A total of 19 papers met our inclusion criteria. Sixteen studies used qualitative evaluation methods and the rest both qualitative and quantitative. In total 42 CPOE design aspects were identified and categorized in seven groups: 1) documentation and data entry components, 2) alerting, 3) visual clues and icons, 4) drop-down lists and menus, 5) safeguards, 6) screen displays, and 7) auxiliary functions. Conclusions: Beside the range of functionalities provided by a CPOE system, their subtle design is important to increase physicians’ adoption and to reduce medication errors. This requires continuous evaluations to investigate whether interfaces of CPOE systems follow normal flow of actions in the ordering process and if they are cognitively easy to understand and use for physicians. This paper provides general recommendations for CPOE (re)design based on the characteristics of CPOE design aspects found.