This study will examine the risks of workplace exposure to benzene, a substance known to lead to cancer of the blood and possibly of the lungs. It is used widely in industries and is a contaminant in the environment. Researchers from the National Cancer Institute and the China Center for Disease Control (formerly Chinese Academy of Preventive Medicine) had done previous studies of workers in manufacturing industries in China of people who worked at least 1 day from 1972 to 1987 in 12 cities in that country. Data were collected of approximately 75,000 workers exposed to benzene and 35,000 who were not, with the purpose of investigating the relationship between benzene exposure and cancer risk. For workers exposed to benzene, there was a significant risk of cancer affecting the blood cells and a 1.8-fold excess of lung cancer among them. This study will expand those findings and also identify the effects of benzene amounts and whether there is a genetic tendency for benzene poisoning. About 3,860 benzene-exposed workers from the 12 cities will be interviewed. Next-of-kin of deceased workers, and a subcohort (additional grouping) of participants will serve as a control group in the research.