Abstract: Objective To investigate the effect of benzo(a)pyrene exposure on learning and memory of adult rats by determination of gene expression in the hippocampus. Methods Eighteen healthy male rats of clean class were randomly divided into toxic exposure and vehicle group.The gene chip technigue was adopted in gene expression profile analysis.The genes with significantly different expression were selected from differential genes and then analyzed with real-time PCR. Results Totally 417 genes exhibited differential expression between exposure group and vehicle group.The expression of 125 genes was up-regulated and 292 genes was dow n-regulated.The results of real-time PCR were coincided well with the cDNA microarray data. Conclusion The regulation of genes may be involved in the effect of benzo(a)pyrene on learning and memory in rat.