Nathan Shock, the leader of the NIH’s gerontology program from 1941 to 1976, played a pivotal role in creating the science of aging as a research field in America. By illustrating his works, I explore how his efforts to biomedicalize aging were linked to the identity and agenda of gerontology as a multidisciplinary scientific field. Indeed, “biomedicalization” is understood in many ways. Whereas it was often equated to molecular reductionism, Peter Keating, Albert Cambrosio, and Adele Clarke have shown that biomedicalization involves a set of more complex changes in laboratories, clinics, and patients’ social worlds with a deep cultural repercussion. According to them, patients were not necessarily passive subjects in biomedical enterprises. This paper will depict how this character of biomedicine resonated with Shock and other gerontologists’ works for more active and productive old age. I first discuss how Shock tried to find the physiological and biochemical mechanism of aging using model organisms, biomolecules, and senior patients in the Baltimore City Hospitals. Then I illuminate how this work was placed in a broader social context associated with the elderly’s continued social participation, industrial productivity, and health management, which were the critical agendas of early American gerontologists who worked to address these problems through their multidisciplinary organizations. This explains, I claim, his unique choice of publishable results, the initiation of the Baltimore Longitudinal Study of Aging, and his continued effort to communicate with regional gerontology groups comprised mostly of educated laymen interested in science.