The authors examined the mortality experience of employees whose work assignments involved development or production of styrene-based products. To investigate potential relationships between mortality and work exposure in the diverse chemical operations under study, a multiple agent approach to exposure categorization was adopted. Mortality was less than that of the corresponding U.S. white male population and was consistent with that of an industrial comparison group. Although deaths due to malignant neoplasms were fewer than expected for the total cohort, an increase in lymphatic leukemia was observed among a subgroup of employees who had exposure to polymer extrusion fumes, solvents, and colorants. However, no relationship was found with duration or intensity of exposures experiences by these employees, and the etiology of the lymphatic leukemias was not established. The approach used to characterize exposure in this study may have application in other epidemiologic investigations involving complex work environments.