The host immune response plays a major role in colorectal carcinoma (CRC) progression. A mechanism of tumor immune escape might involve expression of the human leucocyte antigen (HLA)-E/b2m on tumor cells. The inhibitory effect of HLA-E/ b2m on CD81 cytotoxic T lymphocytes and natural killer (NK) cells is mediated by the main HLA-E receptor CD94/NKG2A. As the pathophysiological relevance of this mechanism in CRC remains unknown, this prompted us to examine, in situ, in a series of 80 CRC (i) the HLA-E and b2m coexpression by tumor cells, (ii) the density of CD81, cytotoxic, CD2441 and NKP461 intraepithelial tumor-infiltrating lymphocyte (IEL-TIL) and (iii) the expression of CD94/NKG2 receptor on IEL-TIL. These data were then correlated to patient survival. We provided (i) the in situ demonstration of HLA-E/b2m overexpression by tumor cells in 21% of CRC characterized by an overrepresentation of signet ring cell carcinomas, mucinous carcinomas and medullary carcinomas, (ii) the significant association between HLA-E/b2m overexpression by tumor cells and increased density of CD81 cytotoxic, CD2441 and CD941 IEL-TIL and (iii) finally, the unfavorable prognosis associated with HLA-E/b2m overexpression by tumor cells. Our findings show that HLA-E/b2m overexpression is a surrogate marker of poor prognosis and point to a novel mechanism of tumor immune escape in CRC in restraining inhibitory IEL-TIL.