A worthwhile medical update on current health concerns from the editors of the popular Harvard Medical School Health Letter. Much of this material originally appeared in that publication, and has been updated and expanded here. The editors group pieces into eight sections, on ""Basic Maintenance"" (fitness, weight, nutrition), ""Reducing the Risks"" (cigarettes, alcohol, other drugs), environmental hazards, ""On the Surface"" (skin, eyes, nails, teeth, hair), sexual matters, stress, ""The Big Three"" (heart disease, stroke, cancer), and, finally, ""Dealing With the Medical Establishment."" There is plenty here on hot topics: we learn, for instance, that ""For an American, the average cancer risk from radon is estimated as being in the range of 0.1-0.9%, which is low compared to the lifetime risk from smoking, judged to be about 25%, or driving a car, 1-2%."" But it is high compared to other risks regulated by the Environmental Protection Agency, and the editors let us know how to find out a household's particular risk, and what to do if it's high (including possible structural alterations to be made on the house). And the word here on AIDS: ""Ultimately, a vaccine will be the surest way to prevent infection""; in the meantime, much remains to be learned about prevention. The authors quite correctly dismiss a popular slogan: "" 'Knowing your partner' is not as easy as it sounds. Establishing whether a partner has been, or is likely to have been, exposed to AIDS is very difficult."" Until we know more, they adequately cover the current best precautions (all quite familiar by now). Throughout, this is clear, current information told in a forthright manner.