To study the difference in gene expression between oral squamous cell carcinoma tissue and their surrounding normal tissue by microarray so as to investigate the preliminary mechanism of pathogenesis of oral cancer.The tissues from 5 patients with oral squamous cell carcinoma tissue and their surrounding normal tissue from the same patients were analyzed by cDNA microarray technology(including 4124 genes). Total RNAs were isolated from two tissues, and then were reversely transcribed to cDNAs with the incorporations of fluorescent dUTP,for preparing the hybridization probes. The mixed probes were then hybridized to the cDNA microarray. After high-stringent washing, the cDNA microarray was scanned for the fluorescent signals and showed the differences between the two tissues. Bioinformatical analysis of those genes had been performed.Among the 4124 target genes, there were 37(0.89%)genes whose expression levels differed between the carcinoma and their surrounding normal tissues in all 5 cases. Bioinformatical analysis of those genes suggested that they may be related to the multistep process of carcinogenesis.cDNA microarray technique can simultaneously screen the different expressions of genes from 2 different kinds of tissue. Further analysis of the obtained genes will help to understand the molecular mechanism of malignant carcinoma.