Colorectal cancer (CRC) is one of the best studied cancers. It is easily accessible and develops slowly over several years from premalignant lesions (adenomatous polyps) to invasive cancers. The key molecular events in this sequence have been characterized. Different screening strategies have proven to be effective in lowering both the mortality and the incidence of CRC. Nevertheless, CRC is still the second leading cause of cancer-related deaths for both men and women in the USA and other Western countries. An estimated 130 000 new cases and more than 50 000 deaths have been diagnosed in the USA in 2000. Surgical resection remains the only curative treatment, and the likelihood of cure is greater when the disease is detected at an early stage. Hereditary non-polyposis colorectal cancer (HNPCC) and the different polyposis syndromes such as familial adenomatous polyposis (FAP) or Peutz-Jeghers disease are rare causes of CRC but have been a major focus of research in past years, helping with the understanding of the molecular events in carcinogenesis. This review summarizes our current knowledge of the pathogenesis and management of colorectal polyps and polyposis syndromes as well as sporadic CRC.