The story of a small group of scientists whose ideas are coming together to shape current theories and therapies for cancer. In his focus on the clinicians, Sylvester (The Gene Age) notes that most credit the gains in cancer cures to earlier diagnosis of the disease. They are quick to emphasize the overwhelming importance of prevention (for which read ""Don't Smoke""). The basic scientists, on the other hand, are trying to fathom, at the molecular level, the step-by-step changes that transform a normal cell into a tumorous one. Following that change comes the still more critical transformation that enables certain tumor cells to leave their home base and invade other tissues, causing the metastases that so commonly lead to death. Sylvester's account begins with an interweaving of three seemingly contending theories: that cancer is caused by environmental carcinogens; that cancer is genetic; that cancer is caused by viruses. During the 1960's and 70's, the viral link to cancer reigned because viruses were known to cause cancers in lower animals. However, even with all the ""War on Cancer"" money poured into research, a bona-fide human cancer virus remained elusive. Then came the discovery of human T cell leukemia virus 1 (HTLV-1) by Robert Gallo of the National Cancer Institute. (Later Gallo found the HTLV 111 virus that causes AIDS.) About the same time came the discovery of ""protoncogenes,"" human genes present in every cell that, under certain conditions, could be altered and ""turned on,"" causing a cell to multiply indefinitely. It was then established that some viruses could pick up these human genes as part of their own gene complement and later, when infecting human cells, trigger cell transformation. However, still other genetic changes are necessary to enable a cell to cross tissue barriers, to elude defense mechanisms, and seed cancers elsewhere in the body. All the details and the colorful personalities that supplied them are well presented in this up-to-date reporting of front-line science. The reader would do well to remember the implicit message, however: while scientists are learning much about the life history and life style of human cells in health and disease, the answer to cancer is still prevention, not cure.