A computerized medical record changes the way a clinician practices medicine by presenting data about patients in multiple organized formats. A computerized record can be used to make it more difficult to overlook important findings. The computer can improve communication by informing both the patient and referring physicians of new data as they become available. Computer graphics or algorithms can be used to emphasize subtle trends. A computer data base can be used to aggregate data about selected patients to provide information about the natural history of disease and effect of treatment.