Strategies to prevent or reverse cancer promotion are described. One strategy, involving the screening and prompt treatment of small lung cancers, is proposed as a study to be tested in occupational groups with very high risk, specifically asbestos-exposed shipyard workers who smoke cigarettes. The relative risk can be assigned on the basis of(l) age, (2) years since first asbestos exposure, and (3) cigarette smoking amount, recency of cessation and age at onset. Proposed surveillance would be chest x-ray films at 4-month intervals and sputum cytology in current smokers and those within 10 years of cessation. Means of detection, such as monoclonal antibody tests for adenocarcinoma and other marker molecules, would be explored. Prompt conventional treatment would be assured. Other inquiries would be directed at new treatment, such as using targeted molecules directed at surface antigens.