We systematically reviewed 15 previous case-control and cohort studies that examined egg consumption as a risk factor for cancers of the colon andrectum. Nine of the 11 studies of colon cancer reported risk estimates consistent with a positive association; in three of these studies the association was statistically significant. The positive association for egg consumption was generally stronger for females than for males, and for cancer of the proximal, rather than distal colon. Six of eight studies of cancer of the rectum reported risk estimates consistent with a positive association; in two of these studies the association was statistically significant. Notably, in every study that met specific design criteria (defined a priori), risk estimates were consistent with a positive association. Two studies reported seven- to eight-fold increases in risk with high egg consumption. In some studies, positive associations remained after adjustment for intakes of macronutrients or for other food groups. The presence of a variety of bioactive compounds, including cholesterol, lends biological plausibility to a role of egg consumption in the aetiology of colorectal cancer.