Despite its widespread use in agriculture, data about cyanamide-induced genotoxicity are scanty, and its genotoxic potential was considered equivocal in vitro. Hence, the current study was carried out to evaluate the in vivo genotoxic potential of hydrogen cyanamide to complement the earlier in vitro research work. Thirty adult male rats were randomly assigned into 3 equal groups. Group I rats served as a control. Animals of groups II and III received hydrogen cyanamide in a dose of 10 and 20 mg/kg body weight/day respectively. All animals were treated by oral gavage, once daily, for 28 days. As end points, chromosomal aberrations, micronucleated polychromatic erythrocytes, mitotic index and polychromatic/normochromatic cell ratio in the animals' bone marrow cells were analyzed. Negative results were obtained regarding the presence of chromosome aberrations and micronuclei in each of the lowdose and high-dose cyanamide-treated rats compared to the controls. Also, cyanamide treatment did not reduce the mitotic index or polychromatic/normochromatic cell ratio in the exposed animals. This study found that hydrogen cyanamide exposure had no genotoxic potential in rat bone marrow cells in the doses used and under the conditions of the performed assays.