A significant proportion of the leukemias, particularly acute nonlymphocytic leukemia (ANLL) may be due to environmental or occupational exposures. ANLL and acute lymphocytic leukemia (ALL) may each be comprised of many different diseases with specific immunologic and cytogenetic features, but with common clinical appearance. There are data to suggest that risk factors may be specific to subgroups of ANLL and ALL defined by these features. A study is being conducted to address the potential for enhanced risk factor detection in well-characterized subgroups of leukemia patients. The study was motivated, in part, by clinical reports suggesting that leukemia patients with specific chromosome changes in bone marrow were more likely than other leukemia patients to have had prior chemotherapy or occupational exposure to chemicals. Using a case-control design, as many as 550 adults with ANLL and 150 adults with ALL who enroll for treatment in first line treatment protocols sponsored by a cooperative cancer treatment group are being studied to evaluate the leukemia risk associated with a variety of environmental and occupational exposures. Patients with leukemia are identified at diagnosis and interviewed by telephone while they are still hospitalized regarding exposure to solvents and chemicals, active and passive smoking, use of hair dyes, irradiation, and family history of certain diseases. Healthy comparison subjects chosen by random telephone screening are also interviewed. Cytogenetic studies being done by the cooperative group are used to classify patients according to the presence or absence of particular chromosomal abnormalities, and risk factors for specific subgroups of patients will be evaluated. Risk factors will also be correlated with other clinical and laboratory parameters such as FAB classification and immunologic phenotype. Over 470 patients and 130 controls have been enrolled to date.