Cantwell, a dermatologist and cancer researcher, takes issue with current medical thinking to argue that AIDS, and perhaps many cancers, are caused by bacterial microbes, rather than viruses. Pleading that researchers not focus exclusively on the virus theory, he suggests that the bacteria responsible for AIDS and cancers takes different forms at different stages of its life cycle--sometimes resembling a virus, sometimes other, familiar bacteria--and thus eludes discovery. Using his theory to postulate how the disease can manifest itself so differently in each victim, Cantwell traces both the epidemiologic history of AIDS and its associated disorders (Kaposi's sarcoma, cytomegalovirus, and others), and its development within the individual host. He makes his case understandable--readers will not get bogged down in statistics or theory--and does not neglect the human tragedies involved. The final determination will of course be made elsewhere, and at the moment Cantwell's opinion is an unpopular minority view. (For the majority view, see Fettner and Check, The Truth About AIDS, p. 339; for advice, consult Siegal and Siegal, AIDS: The Medical Mystery, p. 143.) This is an intriguing alternative, nonetheless, for the scientifically curious--and a still-unsolved case for aficionados of medical mysteries.