Given the many efforts currently under way to develop standards for electronic medical records, it is important to step back and reexamine the fundamental principles which should underlie a model of the electronic medical record. This paper presents an analysis based on the experience in developing the PEN & PAD prototype clinical workstation. The fundamental contention is that the requirements for a medical record must be grounded in its use for patient care. The basic requirement is that it be a faithful record of what clinicians have heard, seen, thought, and done. The other requirements for a medical record, e.g., that it be attributable and permanent, follow naturally from this view. We use the criteria developed to re-examine Weed's Problem Oriented Medical Record and also relate the criteria to secondary uses of the medical record for population data, communications and decision support.