ABSTRACT:Research in aging is now becoming firmly rooted in the scientific method. If it receives the support it deserves, it may produce the next major advance in biology. This article summarizes some of the biological aspects of the field including hypotheses, the aging of cultured human cells, the inverse relationship between donor age and cell longevity, the senescence of cultured normal cells derived from different animal species, the latent period of explanted cells versus donor age, progeria and Werner's syndrome, and the future of gerontological research. Life expectancy at birth has increased in recent years, but at age 65–70 it has remained virtually fixed. The human lifespan will not be changed significantly until the underlying biological causes of senescence are slowed or stopped. Since support for research in this field is almost non‐existent, it is more important to concentrate our efforts on increasing research support for gerontology than on increasing the mean lifespan of man. Without the former, the latter will never be impro