Objective:To investigate the potential role of orotate phosphoribosyltransferase(OPRT),dihydropyrimidine dehydrogenase(DPYD) and thymidylate synthase(TS) in serving as biomarkers for drug sensitivity in primary gastric cancer. Methods:Viable tumor cells obtained from the samples of forty-seven patients with gastric carcinoma were tested for their sensitivity to 5-fluorouracil using ATP-TCA assay. Reverse transcription-PCR was used to measure the mRNA level of the three 5-fluorouracil related genes. Results:OPRT mRNA level was positively correlated with the sensitivity to 5-fluorouracil (r=0.744,P=0.001) while TS mRNA level was negatively correlated with the sensitivity(r=-0.375,P=0.009). No significant association was observed between DPYD expression and 5-fluorouracil sensitivity (r=-0.159,P=0.287). Conclusion:Detection of the expression level of OPRT and TS mRNA in gastric cancer might be of good value for predicting the sensitivity to 5-fluorouracil.