As 70–80% of MSI-H cancers appear to be related to the epigenetic inactivation of MLH1 (Cunningham et al, 1998; Herman et al, 1998), in our samples, the production of amplifiable mRNA for MLH1 suggests a post-transcriptional mechanism as the basis for reduced MLH1 function in these cancers. This evidence concerns the gene MLH1 and cancer.