Ethylene dibromide, a suspected carcinogen, and ethylene dichloride are commonly used in leaded gasoline as scavengers. Ethylene dibromide emission rates were determined from seven automobiles which had a wide range of control devices, ranging from totally uncontrolled to evaporative and catalytic emission controls. The vehicles were operated over a variety of cycles to simulate the normally encountered range of driving conditions. Evaporative losses were also measured. Tailpipe emission rates varied from 0 to 1300 micrograms ethylene dibromide per mile depending upon the control devices present and the operating cycle. Evaporative emission of ethylene dibromide ranged from 0.03 to 0.4 micrograms per mile equivalent. Emission of other lead-related compounds were sought but not found.The consequences of using leaded fuels in vehicles equipped with catalysts was investigated. Emission rates of ethylene dibromide increased with usage and appeared to depend on catalyst activity.Overall emission rates of ethylene dibromide correlated with hydrocarbon emission rates.