The genotoxicity of ethylene-dibromide (106934) (EDB) was evaluated using in-vivo cytogenetic assays. EDB was injected intraperitoneally (ip) into male CD-1-mice. Based on median lethal doses, EDB concentrations of 42, 84, and 168 milligrams per kilogram (mg/kg) were selected for cytogenetic studies. Bone marrow cells isolated from femora were analyzed for sister chromatid exchange (SCE), chromosomal aberration, and micronucleus formation. The frequencies of the first, second, and third generation metaphases were determined in 100 consecutive metaphase cells from each animal for evaluating cellular proliferation. The incidence of micronucleated cells per 500 polychromatic erythrocytes (PCE) was determined in each animal. The ratio of normochromatic erythrocytes (NCE) to PCE was also calculated to determine the toxic effects of EDB to bone marrow cells. Among the three doses tested, 84 and 168mg/kg EDB yielded 6.09 and 5.47 SCEs per cell, respectively. The number of first, second and third, or subsequent division cells were in close approximation for all treatments and in controls. Following in-vivo exposure to EDB, the group exposed to 42mg/kg had a slight but significant increase in chromosomal aberrations over the negative control group; aberrations consisted of gaps, breaks, and fragments. The number of PCE with micronuclei was not significantly different between the controls and treated cells. The ratio of NCE to PCE was similar between the control and treated animals. The authors conclude that EDB is not an effective genotoxic agent in-vivo in mice.