Few scientists are talented enough to span more than one discipline, especially fields as diverse as medicine and mathematics. But Robert S. Ledley has done just that, with results that have revolutionized the way medical diagnosis is done.

Ledley was born in New York City in 1926, and earned a doctorate in dental surgery (D.D.S.) from New York University at the age of 22. One year later he earned a master's degree in mathematical physics from Columbia University. After brief service in the U.S. Army, Ledley worked at the National Bureau of Standards and at Johns Hopkins University before becoming professor of physiology and biophysics and of radiology at the Georgetown University Medical School in 1970.

Ledley is credited with establishing the field of medical informatics, in which computers and other information technologies aid physicians in the diagnosis and treatment of patients. This foundations of this field lie...