The purpose of this study is to determine the accuracy of some of our present-day clinical instruments, on which the physician relies for important information concerning his patients' status and progress. The study has been limited to the thermometers and urinometers in use at a 500-bed general hospital. The success of modern medicine does not depend on the absolute accuracy of these instruments either for correct diagnoses or for proper management of the patient. The healing art was far along when the physician estimated temperature rise by the laying on of hands. The "urinologists" of former years could roughly discern whether a person's urine was too concentrated or too dilute. Today, however, we have at our fingertips numerous instruments of precision that have rightfully taken the place of guesswork in medicine. Many times a physician comes into the modern hospital and sees on his patients' charts incongruous temperature graphs, weight