Among sessile serrated adenomas (SSAs) with identical histologic features, some never progress whereas others become dysplastic and develop into invasive cancers. Development of the CpG island methylator phenotype (CIMP) is a feature of SSA progression; we examined the CIMP status of 448 SSAs and examined the association with patient outcomes. Overall 190 SSAs were CIMP positive. CIMP positivity was associated with older patient age (P<.001) and proximal polyp site (P<.001), but not with patient sex (P=.94) or polyp size (P=.34).