There are at least three major encyclopedias in the field of aging, all of them general and comprehensive. This new encyclopedia is focused more on health and, as such, is aimed at assisting researchers, students, and practitioners working in the fields of medicine, nursing, epidemiology, public health, health services, and related areas. The topic areas reflect the range covered in the Journal of Aging and Health, which I founded in 1989. There is also a heavy dose of geriatrics with respect to geriatric syndromes and common diseases of aging. The field of health and aging has grown nearly exponentially during recent decades, and I hope this encyclopedia captures some of the excitement of the research enterprise in terms of new findings as well as conceptual developments guiding research, practice, and policy.rn