Dr. Leaf, Chief of Medical Services at Massachusetts General in Boston, and photographer Launois (his contribution to the book is an inset of pictures) traveled to three isolated small regions which have favored longevity to a remarkable degree. Since these are subliterate societies, Dr. Leaf will agree that the figures are ""unverifiable"" and Gallup has further pointed out the frailty of the records. In the Caucasus, primarily in Georgia, there are 4500-5000 centenarians; in Hunza, in the mountains of Pakistan, there's another tribe of oldsters -- but none to be found in the rival state just across the river; and Vilcabamba, Ecuador, is the third site where Dr. Leaf examined and talked to the natives to assess their modus vivendi. The second part of this book discusses sensibly, if non-innovatively, the factors which reduce the degenerative diseases of aging and connect certain possibilities with what had been earlier observed. Perhaps more than the Hunza water or ""God and the climate."" One can Fred correlatives in the low caloric intake or the steep terrain which strengthens the heart or a protein deficiency which might discourage cancer. Beyond diet and exercise, Leaf also discusses the sexual, social and psychological aspects which promote continued well-being -- no stress, a sense of individual worth, etc., etc., while the rest of the world faces the increasing dangers of overpopulation and hunger. He also goes along with the current thinking that as we protract the lives of the very ill, the benefit diminishes as the effort increases. The early material appeared in National Geographic where it attracted, justifiably, considerable attention -- its extension is only corroborative of what we know.