The specific aim of the proposed research is to evaluate the joint etiologic importance of occupational exposures, environmental exposures and cigarette smoking among newly diagnosed cases of adult male leukemia residing in six Texas Gulf Coast counties. All new cases occurring between January 1982 and December 1986 will be included in the study. Cases are identified through a hospital-based ascertainment system and are confirmed for study eligibility through a histopathlogic review. The design is a population-based case-comparison study in which exposure information is obtained through interview. Two comparison subjects are drawn from drivers' license tapes provided to the investigators by the State of Texas, and frequency matched to cases by age and race. The study area contains one of the larget petrochemical complexes in the world, and is well suited for the study of the influence of occupations in these industries. Analysis of the data will be by histologic types of leukemia whenever numbers permit. Interactions among the primary risk factors will be examined by use of the logistic model. Other potentially important factors to be examined include familial aggregation of leukemia and other cancer, prior exposure to therapeutic radiation and chemotherapy, contact with sick pets, and history of viral disease.