In this chapter, it is pointed out that colorectal cancer is a heterogeneous disease. The case is made for a ‘serrated pathway’ of neoplasia that would evolve relatively rapidly through the early acquisition of DNA instability. DNA hypermethylation is likely to be of critical importance in driving this pathway. Inhibition of apoptosis is conceived as the first step. Thereafter, methylation of one of several DNA repair genes would result in a state of tolerated hypermutability. It remains to be shown whether this model applies to a small subset of colorectal cancers or in fact explains the great majority given the overall low risk of progression for an individual adenoma initiated by mutation of APC.