HNPCC patient is an individual with a personal history of RER plus HNPCC related malignancy AND; meets the Amsterdam criteria or modified Amsterdam criteria (an HNPCC associated extracolonic cancer may be substituted for one of the three colorectal cases in one family otherwise required by these criteria) OR; having a definite mutation of one of the HNPCC - related genes identified by gene sequencing or other method of reliability. This includes gene status determined through segregation analysis in cases in which "direct" testing yields no alteration.