A review of pertinent data and a preliminary report of NIOSH study findings regarding the toxic interaction of ethylene-dibromide (106934) (EDB) and disulfiram (97778) (DSF) were presented. Ethylene-dibromide has been used in leaded fuel, as an intermediate in pharmaceutical and dye synthesis, as a soil, grain and fruit fumigant and as a solvent. About 9,000 workers had potential exposure to EDB during its use; approximately 650,000 gasoline station attendants also had the potential for exposure to very low levels of EDB. EDB alone has been found to be a very toxic compound. Adverse health effects as a result of chronic exposure may include cancer induction, sterility, and malformations and heritable changes in offspring. DSF has been used as an alcohol deterrent drug, as an accelerator in rubber manufacturing processes, and as a fungicide and insecticide. About 70,000 workers had potential occupational exposure to DSF, and about 100,000 people may receive DSF in alcoholism control programs. The limited data available on DSF have not permitted an evaluation of its carcinogenicity. In the NIOSH study, four groups of 96 Sprague- Dawley-rats (48 male, 48 female) were exposed to either filtered air plus control diet (untreated group); filtered air plus diet containing 0.05 percent DSF (DSF group); inhalation of 20 part per million EDB 6 hours/day, 5 days/week plus control diet (EDB group); or EDB inhalation plus DSF diet (EDB+DSF group). After 13 months of exposure 92 of the 96 rats in the EDB+DSF group either died or were terminated due to tumor development compared to 24 in the EDB group, 5 in the DSF group, and 3 in the untreated group. Tumors observed in the EDB+DSF group included hemangiosarcomas of the liver, spleen, and kidney, and an increased incidence of tumors at sites where tumors often occur spontaneously. NIOSH recommends that no worker be exposed to both ethylene-dibromide and disulfiram.