Abstract: Objective To investigate the synergistic effect of benzoapyrene(BaP)and lead on learning and memory of mice.Methods Eighty male Kunming mice were randomly divided into 10 groups:control group,vehicle control(sesame oil),low(5.4 mg/L)and high(54 mg/L)dose lead acetate groups,low(0.5 mg/kg bw)and high(5 mg/kg bw)dose BaP groups,low dose lead+low dose BaP group,low dose lead+high dose BaP group,high dose lead+low dose BaP group,and high dose lead+high dose BaP group.The capability of learning and memory of the mice were measured with Morris water maze(MWM)test and the DNA damage of neuron in the hippocampus was assessed with single-cell gel electrophoresis(SCGE).Results Compared with the control groups,both BaP- and lead-exposed animals showed significant increase in escape latency(25.66±2.93,28.43±3.24,2.56±2.69,33.54±3.82,28.52±3.25,43.57±4.97,40.26±4.59,and 54.54±6.22, all P<0.001);however,the numbers crossing the exact location of the platform and the time spent in the target quadrant were significantly decreased(all P<0.001)in MWM test.The animals in experimental groups also showed a significant increase in the percentage of DNA in tail (0.09%,0.15%,0.12%,0.21%,0.17%,0.31%,0.31%,and 0.51%)compared with those of the control groups(0.08%,F=9.823,P=0.001;F=5.226,P=0.012).Conclusion The combination of BaP and lead exposure could induce spatial learning and memory impairments synergistically in mice and the mechanisms of the synergistic effects may be due to oxidative stress injury.