Medical errors are often associated with inadequate cognitive processing that is based upon impaired access to information.1 Understanding the information needs of nurses and physicians' when using a clinical information system (CIS) is difficult largely because there are few systematic attempts made to do so. We collected 15.5 hours of data of nurses and physicians' CIS interactions in three clinical environments (cardiac ICU, a general medical/surgical nursing, and an ambulatory clinic). We accomplished this through observational, cognitive-based methods (e.g., thinking aloud during interaction) and the video capturing of events with a portable usability laboratory.2 We developed a systematic approach to identify and define in-context clinical information needs while using a CIS, and determine how to categorize and code such events. 3