The story of the important viral hepatitis research conducted at St. Vincent's Hospital and Medical Center in New York City warrants a chapter of its own. My interest in viral hepatitis was whetted in 1942, when I volunteered for military duty in WW II and was awaiting my appointment as a captain in the Medical Corps of the Army of the United States and the call to active duty. At the time I was on the teaching staff of the Columbia University College of Physicians and Surgeons and in the private practice of general internal medicine and also director of the personnel medical department of the Columbia-Presbyterian Medical Center. Dr. Fred Soper of the Rockefeller Foundation, a renowned expert and investigator in yellow fever, came to the Medical Center to lecture on an epidemic of jaundice that had struck thousands of newly mobilized recruits in military service. I sat on the edge of my seat in the amphitheater as Dr. Soper regaled us with the tantalizing mystery of this ailment and its cause. He had been called in as a consultant because most of the cases had appeared in men who had received yellow fever vaccine injections. Was it a variant of yellow fever or was it something else? Fortunately, the illness was usually mild. Needle liver biopsies were not feasible at the time and routine biochemical studies were primitive and not very helpful. Of some value were the autopsy findings in a few soldiers who had been vaccinated against yellow fever and had died in military-training accidents. These showed no evidence of yellow fever but were positive for a mild form of hepatitis. Soon it was determined that only certain batches of the yellow fever vaccine caused the hepatitis. This research project was facilitated by the fact that the only organization authorized to manufacture the vaccine was the International Health Division of the Rockefeller Foundation. Each vial or lot of vaccine was numbered and the mili- tary kept records of each lot and persons vaccinated. By the late fall of 1941, the surgeon general and his advisors, in anticipation of the spread of WW II to areas where yellow fever was endemic, had recommended and started full-scale military use of the vaccine.