OR decades, science writers have referred to the "mystery" of cancer. This regrettable characterization is, at f7 _ 2best, half true, reflecting the utter confusion between g cause" and "cure" with respect to cancer. There is, indeed, a great deal of mystery as regards the search for (K#*4s) effective cancer cures. In fact, during the past twenty years of intensive pursuit of cancer cures, the survival rates for the most common types of major cancers-lung cancer, breast cancer, and cancer of the colon-have remained almost unchanged (1). But what about the causes of cancer? Here, there is less mystery. Actually, our accumulated knowledge about the causes of cancer is very impressive, stretching back over 200 years. In 1775, a London physician, Percival Pott, first noted the apparent connection between exposure to coal soot among chimney sweeps and the subsequent high incidence of cancer of the scrotum among the young boys compelled to do this terrible work. Dr. Pott postulated that this malignancy, which was so common among chimney sweeps, must be attributable to the soot amassed on and within their bodies. The perceptive doctor was absolutely right, but it wasn't until this century that scientists isolated one of the cancer-causing chemicals present in coal soot-benzo (a)pyrene, the same substance that contaminates the air in many large cities and is deemed partially responsible for excessive rates of lung cancer among urban dwellers. In 1822, another English physician, J. A. Paris, identified the connection between arsenic and skin cancer, a cause-and-effect relationship that is beyond dispute today. By the end of the nineteenth century, with the onrushing advance of the modern Industrial Age, scientists and physicians were just beginning to recognize the chemical origins of cancer: skin cancer among workers in the Scottish shale industry; cancer of the lip, larynx, and lung among workers handling coal tar and pitch; lung cancer, liver cancer, and bone cancer among miners of radioactive ore. In the 1930S