Abstract: To determine the genetic injury on the root-tip cells of Vicia faba caused by lead in water, a micronucleus assay was conducted.The genotoxic effect of lead acetate in the concentrations ranging from 0.5 mg·L^-1 to 30 mg·L^-1 were monitored and pollution indices calculated. The results showed that micronuclei in the cells increased with increasing lead concentration. When the cells were exposed to lead acetate at the concentration of 30.0 mg·L^-1 for 6 h, the number of micronuclei in the cells were significantly higher than that in control (P < 0.05).The pollution index was greater than 3.5, which was considered as a heavily polluted condition. Moreover, in the cases where the cells were treated with lead concentrations at 1.0-30.0 mg·L^-1 for 12 h, similar results were observed at an extremely significant level(P < 0.01). At a same lead concentration, the 12 h treatments affected the cells significantly greater than the 6 h treatments. However, the difference was only at a significant level(P < 0.05) for 1 mg Pb·L^-1. It seemed apparent that lead was absorbed to causegenetic injury to cells in the roots of V. faba, and the toxicity increased with dosage and time of the exposure.