Gelboin subsequently earned a PhD in Biochemistry and Oncology from the McArdle Laboratory for Cancer Research at the University of Wisconsin-Madison, where he was mentored by James and Elizabeth Miller.[2][4] Gelboin's research at NCI centered on working out how the body metabolizes environmental carcinogens, for example, benzopyrene, which occurs in tobacco smoke, auto exhaust, and other smoke-producing sources.Gelboin pioneered early research on how chemicals, drugs, and carcinogens are metabolized by enzymes in small lipid vesicles (microsomes) in the liver.[2] Gelboin has left behind a number of former colleagues and trainees now working at laboratories around the world, many of whom have achieved leadership positions in the areas of drug and carcinogen metabolism and who continue to carry out his legacy of scientific inquiry.One of his publications, a paper on development of a widely used assay for a key enzyme in the metabolism of carcinogens, became an Institute for Scientific Exchange Citation Classic.