Animal studies have indicated the carcinogenic potential of ethylene dibromide (EDB). Examination of the mortality experience of employees exposed to EDB in two production units operated from 1942 to 1969 and from the mid-1920s to 1976, respectively, showed that in the first unit two deaths from malignant neoplasms were observed against 3.6 expected (based on US white male mortality), and in the second unit, where there was potential exposure to various organic bromide products, five deaths from malignant neoplasms (2.2 expected) were observed. Findings of this investigation neither rule out nor establish EDB to be a human carcinogen. Far fewer malignant neoplasms, however, have been observed than might have been expected from a direct extrapolation of data obtained from experiments on animals.