We examine an important part of the medical record that has not been studied extensively: physicians’ clinical notes. These notes constitute an explanatory medical narrative that documents the patient’s illness trajectory by combining each physician’s notes into a common text. Although several prior CSCW studies have addressed the role of the medical record in patient care, they have not dealt specifically with the role, structure, and content of these notes. In this article, we present a detailed analysis of a set of physicians’ clinical notes recording the acute hospitalization and subsequent treatment of a patient with chronic heart disease. We show that clinical notes are highly structured and conventionalized texts that promote conciseness while at the same time allowing physicians to express themselves in a precise and nuanced way. Based on this analysis, we argue that physicians’ clinical notes form the core of the medical record. They serve both as a ‘tool for thinking’ for the individual physician, enabling him or her to make sense of the patient’s past history and current condition, and as a coordinative artifact used by physicians, nurses, and other health care professionals. We conclude by discussing the implications of this research for the design of Electronic Medical Record (EMR) systems.