In 1983, lung cancer exceeded breast cancer as the leading cause of death in American women. Between 1950 and 1985 there was a 500% increase in lung cancer deaths in women, and this trend is not expected to improve in the next decade. There is no corresponding increase in the overall incidence of lung cancer in the general population of the United States. Cigarette smoking is clearly the primary risk factor in this group and the role of passive smoking remains controversial. Various other etiologic factors, including a shift in occupational exposure, may play a minor role in the development of lung cancer in years after smoking cessation. If the incidence of smoking in American women was reduced to pre-1950 levels, it is estimated that lung cancer in women would once again become a rare finding after the year 2000.