DESIGN. A cross-sectional study involving 100 patients with RA were enrolled from TCVGH. Genotypes in methylenetetrahydrofolate reductase (MTHFR677C>T), tandem repeat polymorphism in thymidylate synthase enhancer region (TSER) and folylpoly-gamma-glutamate synthetase (FPGS1901T>C) were determined by RFLP or pyrosequencing.