~ lnpufi N °..~~..'. ~.............. Smoking and Lung Cancer: Scientific Challenges and Opportunities'

Cigarette smokina has been conclusively established as the leading cause of lung cancer in men and women (1-3). The progress made in our understanding of the epidemiology of smoking and lung cancer and the delineation of major mechanisms of tobacco carcinogenesis (3-5) may have given the impression that future research is no lonlaer needed and that all that remains to be done is the effective application of preventive measures. This impression requires revision, because several key questions on smoking and lung cancer are still awaiting answers. In this overview we will discuss some of these unresolved issues. They include: (a) the change in the distribution of the major histo-lojical types of lung cancer during the past four decades, and a gender-related difference in the occurrence of squamous cell carci-noma and adenocarcinoma of the lung; (b) the differences in the lung cancer incidence rates between American and Japanese smokers and between African-American and White American male smokers; (c) the debated issues on the association between passive (involuntary) smoking and lung cancer; and (d) monitoring of cigarettes and smokers. Additional challenges arising from recent and ongoing epidemio-logical investigations include a thorough study on the possible higher risk for adenocarcinoma of the lung amona men and women with lower body weight (6, 7). However,,ve will limit this review to the four aspects listed above