Aging is one of the most serious and costly health problems in the Western world. A disproportionate amount of the available health care capability is devoted to the health care of the aged and the cost of this care is soaring. Viewed in wide perspective, aging presents two problems for the researcher's consideration. First is that of providing the most efficacious therapeutic regi- mens and the best possible care for those already in their latter years. The second is to determine the cause or causes for senes- cence and all its attendant problems in order to decrease the im- pact of senescence on general health and well being. This volume is aimed at examining possible relationships be- tween biological time structure and aging and ways by which these interrelationships might be examined in terms of both the causes of senescence and the management of health problems of the elderly. The purpose of the volume is to stir the interests of chronobiolo- gists in gerontology and those of gerontologists and geriatricians in chronobiology.