The autosomal dominant inherited Lynch syndrome, also referred to as hereditary nonpolyposis colorectal cancer (HNPCC) is the most common inheritable colorectal carcinoma syndrome, accounting for up to 3% of colorectal cancers in western populations. First-degree relatives of Lynch syndrome patients have a 50% risk of also being a gene carrier. The family history of Lynch syndrome families is characterized by the early onset of colorectal cancer, a certain range of extracolonic malignancies as well as a higher incidence of synchronous and metachronous colorectal cancer. Without a suitable cancer prevention program there is a shorter life expectancy for Lynch syndrome patients in comparison to the general population. The German HNPCC consortium ( http://www.hnpcc.de ) is a collaboration of six clinical university centers, together with a reference pathology, gastroenterology, oncology and a central biometrics department which have been involved in the interdisciplinary medical care of patients with Lynch syndrome since 1999. Furthermore, the German HNPCC consortium is engaged in the development and optimization of standards for clinical identification, diagnostics and surveillance of patients with Lynch syndrome.