The study population consisted of 140 consecutive colorectal cancer patients, inhabitants of the city of Szczecin, north west Poland, who were histopathologically diagnosed in the period of 2 years 1991 1992. Family history was obtained in 124 (88.6%) of patients. A definitive diagnosis of HNPCC was established if requirements of the International Collaborative Group on HNPCC (ICG HNPCC) were met. Suspected HNPCC were recognised according to criteria described by Ponz de Leon or Mecklin or Kunitomo. HNPCC as defined by International Collaborative Group on HNPCC was identified in 2 (1.6%) families. Suspected HNPCC were recognised in 16.9%, 3.2% and 4.0% of patients if Ponz de Leon or Mecklin or Kunitomo criteria were applied, respectively. In our series in 19 of 124 cases, colorectal carcinomas were diagnosed in patients under 50 years of age. Only in one of these cases, features characteristic of HNPCC other than young age were found which suggests that in our region the frequency of somatic or germ line de novo mutations in genes predisposing to colorectal cancer may be high. Our results suggest that the frequency of HNPCC inherited from ancestors in Poland and other countries is approximately similar and this syndrome is common disease everywhere.