Aberrant DNA methylation changes can be detected in virtually all CRC tumours [2], but it is the transcriptional silencing of MLH1 through promoter hypermethylation (referred to as MLH1 methylation) that is one of the most clinically important and well-characterised epigenetic events, seen in 10–20% of all CRCs [4]. The gene discussed is MLH1; the disease is colorectal carcinoma.