To investigate the expression of HLA gene mRNA in peripheral blood mononuclear cell (PBMC) of patients with gastric cancer. HLA-A, -B, -DP, -DR, -G mRNA expression levels in 43 patients and 22 healthy individuals were performed by reverse transcriptase polymerase chain reaction(RT-PCR) and real-time RT-PCR. The expressions of HLA-A, -B,-G mRNA in gastric cancer group were significantly lower than that in healthy group, while there was no significant difference in HLA-DP, -DR between two groups. The expression of HLA-A -B and -G in PBMC weren't associated with the clinical staging and histological grading of gastric cancer. While the expression of HLA-G in III + IV grade was lower than that in I+ II grade. HLA-A, -B, -G may play critical roles in the tumor immune response. RT-PCR or real-time PCR may be used as a rapid and simple method to detect HLA gene mRNA expression.