A previous epidemiologic study of the U.S. rubber industry indicated that there has been an excess of leukemia and lymphoma mortality among hourly workers at one styrene-butadiene rubber manufacturing plant. This investigation was a combined industrial hygiene and hematology cross-sectional survey at the same plant. The objectives of the survey were to quantify exposure levels for styrene, butadiene, benzene and toluene, and to relate these levels to hematologic variation. Personal air samples and blood specimens were obtained from 157 production workers. All exposure levels for the four chemicals assayed were well below recommended standards. The higher mean styrene (13.67 ppm) and butadiene (20.03 ppm) concentrations were found in the Tank Farm area; in all other departments the mean levels for the four chemicals were less than 2 ppm. The Tank Farm workers had slightly lower levels of circulating erythrocytes, hemoglobin, platelets and neutrophils, and slightly higher mean corpuscular red cell volumes and neutrophil band counts than the other workers. Overall, in this population there was no pronounced evidence of hematologic abnormality, as determined from examination of peripheral blood.