【Abstract】Objective To investigate the expression of the mRNA of cancer-testis antigen 9 (CT9) gene in hepatocellular carcinoma. Methods The expression of CT9 mRNA was detected through RT-PCR in HCC tissues and their adjacent non-HCC tissues from 45 HCC patients. From CT9 RT-PCR positive products, 3 samples were selected randomly and were sequenced. ResultsCT9 mRNA was detectable in 51.1%(23/45) of HCC samples, and no expression of CT9 mRNA was detected in the adjacent non-HCC tissues. In addition, the RTPCR products were proved to be CT9 cDNA by DNA sequencing. No relationship was found between the expression of CT9 mRNA and clinical factors such as age, sex, tumor size, degree of tumor differentiation, serum αfetoprotein level and infection of hepatitis B virus or hepatitis C virus （Pgt;0.05）. ConclusionCT9 mRNA is expressed with high percentage and specificity in hepatocellular carcinomas. The CT9 gene product is a potential target for antigenspecific immunotherapy of HCC.