The intestinal epithelium is a self-renewing tissue which represents a unique model for studying interconnected cellular processes such as proliferation, differentiation, cell migration and carcinogenesis. Although the stem cells of the intestine have not yet been physically characterized or isolated, data over the past decade have strongly implicated the Wnt/beta-catenin signalling pathway in their maintenance and progression to cancer. This review will (i) describe the distinctive features of the intestinal epithelium in relation to stem-cell function, (ii) illustrate the major genetic alterations that can lead to cancer, and (iii) show how Wnt/beta-catenin signalling controls homoeostasis in this tissue.