This document contains a glossary which defines 275 basic terms frequently used by gerontologists. The glossary is designed for use by a general population, including older persons and their families, students in the field of aging, librarians, medical reporters, health care providers, and others interested in older persons. It was developed to provide a single resource that defines terms used in the field of aging. Common terms used in research and health care are emphasized. Related terms are grouped alphabetically under nine subject categories: (1) aging; (2) research on aging; (3) the body; (4) medicines and drugs; (5) medical problems; (6) women; (7) mental health; (8) social programs and services; and (8) medical specialties. Also included are a table of contents, an index of terms, and a brief introduction. (NB)