Increased blood levels of homocysteine have been found to be associated with inflammatory bowel diseased (IBD) in several studies.^1,2 The main genetic determinant associated with elevated plasma levels of homocysteine (t-Hcys) is the MTHFR 677C→ T gene polymorphism of methylenetetrahydrofolate reductase, a critical enzyme involved in the remethylation pathway of homocysteine.³ An association of the MTHFR 677T allele with IBD has been reported in Northern Europe^1,4 but not in three other series from Italy and France.^5–7 Double heterozygosity MTHFR 677CT+1298AC also produces reduced enzyme activity and increased t-Hcys, but its association with IBD has never been studied. Similarly, the association of IBD with transcobalamin (TCN1 776C→G), a genetic determinant that influences transcobalamin levels and t-Hcys, …