Objective: Colorectal cancer cells with a CD44+ phenotype have been suggested to have tumor-initiating properties with stem cell-like and invasive features, although it is unclear whether their presence within a tumor has clinical implications. We have explored the prevalence of cells with different CD44 phenotypes within colorectal cancer subtypes.Materials and Methods: Immunohistochemistry was used to quantify CD44 expression in 140 human colorectal tumors for which information on other tumor markers was available.Results: A considerable heterogeneity in CD44 expression was seen both between and within tumors. A complete lack of this protein was evident in 35% of the tumors. CD44+cells were detected in 65% of the tumors, ranging in proportion from only a few to close to 100% of tumor cells. The CD44+phenotype was most common in the basal-like subgroup - characterized as negative for ANXA1, and as positive for bcl2 and particularly common in APC defficient tumors, of which 94% contained CD44+cells.Conclusion: We demonstrate an association between APC defficient colorectal cancer and the presence of CD44+cells. Not all basal-like tumors and very few ANXA1 tumors, however, contain CD44+cells, emphasizing that a putative tumorigenic ability may not be confined to cells of this phenotype