Many machine-readable identification systems (MRIS) that can automatically identify patients and their laboratory specimens are described in this paper. It is recommended that greater use be made of bar-code, optical character, or magnetic ink label printers and readers, to permit MRIS of X-ray films, EKGs, EEGs, and other tracings, drugs, and blood-products, as well as for requisitions, forms, charges, reports, and medical records. This technology will contribute greatly to eliminate a major source of error in health care, as well as accelerate the performance of many procedures, control cost by reducing personnel levels, and improve medical care substantially.