Worldwide colorectal cancer (CRC) has a higher incidence rate in men than in women, suggesting a protective role for sex hormones in the development of the disease. Preclinical data supports a role for estrogen and its receptors in the initiation and progression of CRC and establishes that protective effects of estrogen are exerted through ERβ. Hormone replacement therapy (HRT) in postmenopausal women as well as consumption of soy reduces the incidence of CRC. In the Women's Health Initiative (WHI) trial use of HRT in postmenopausal women reduced the risk of colon cancer by 56% (95% CI, 0.38 to 0.81; P=0.003). A recent meta-analysis showed that in females, consumption of soy reduced the risk of colon cancer by 21% (95% CI, 0.03 to 0.35; P=0.026). In this review, utilizing the preclinical data, we translate the findings in the clinical trials and observational studies to define the role of estrogen in the prevention of CRC. We hypothesize that sometime during the tumorigenesis process ERβ expression in colonocytes is lost and the estrogen ligand, HRT or soy products, exerts its effects through preventing this loss. Thus in the adenoma to carcinoma continuum, timing of HRT is a significant determinant of the observed benefit from this intervention. We further argue that the protective effects of estrogen are limited to certain molecular subtypes. Successful development of estrogen modulators for prevention of CRC depends on identification of susceptible CRC population(s). Thus research to better understand the estrogen pathway is fundamental for clinical delivery of these agents.