Using a cohort we have been studying in Linxian since 1985, we examined the relationship between incident ESCC and GCA cancers and three polymorphisms in two genes that code for enzymes that require folate and B(12) as cofactors: methionine synthase reductase (MTRR) A66G and methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C.