Optimism knows no bounds in this fantastic extrapolation from current research on aging. Fossell (Clinical medicine/Michigan State Univ.) foresees a wonderful future in which not only will human aging be reversed but cancer will be vanquished and heart disease, stroke, and Alzheimer's prevented. The key, it seems, is learning how to manipulate the clock of aging, which has now been identified as the telemere, the end segment of DNA on chromosomes. Fossell reports that in the laboratory researchers have been able to reset the telemeric clock in cells. Next, he says, will come development of safe and effective means of doing so in human beings. He cheerfully predicts that within the next ten years telemerase inhibitors, which prevent cells from dividing, will provide a cure for cancer, and by the year 2015 telemerase inducers, which keep cells from aging and thus prevent degenerative diseases, will be available. Fossell devotes most of his text to explaining the basic mechanisms of aging on the cellular level, and he does this adroitly, using black-and-white drawings, simple analogies, and plain English. The consequences of a greatly enhanced life span (the actual number of years remains uncertain) are far less thoroughly considered. The author's predictions of how society might be transformed are diverting but simplistic, touching lightly on, among other things, population growth, the economy, retirement, education, the environment, marriage and the family, and crime and punishment. While acknowledging that there will be some problems, or ""growing pains,"" as he calls them, his view is decidedly rosy, almost Panglossian. Valuable for its lucid explanations of current knowledge about aging, and entertaining in its speculations about the future.