To clone the upstream untranslated region of CYP9G2 from diamondback moth,the genomic walking was performed according to the routine procedure based on PCR amplification using the outer adaptor primer(AP1) and CYP9G2 specific primer(GSP1).After T-A cloning,positive clones were confirmed by nested PCR using the outer adaptor primer(AP2) and CYP9G2 specific primer(GSP2) as forward and reverse primers.Analysis of the upstream DNA sequence of CYP9G2 showed that 5 cis-acting elements existed in the upstream sequence of CYP9G2.One of the elements was a putative initiator of arthropoda,three of them were CAAT-like boxes,and the other one was an antioxidant-response-like element.This kind of genome walking could be used in rapid cloning of the promoters and other upstream regulatory elements in genes that only cDNA sequence was available,mapping of intron/exon junctions,and walking bidirectionally from any sequence-tagged site or expressed sequence tag.The method is simple,reliable and efficient.