OBJECTIVE: The aim of the present study was to examine the clinicopathologic characteristics of Chinese patients with hereditary non‐polyposis colorectal cancer (HNPCC) and those with suspected (atypical) HNPCC.METHODS: Personal and family cancer histories were obtained by reviewing the charts and interviewing the proband and participating relatives. Families were identified and classified into three groups by either the Amsterdam or Japanese criteria for HNPCC. Clinical characteristics including onset, localization, stage of colorectal cancer (CRC), tumor multiplicity, survival and mucinous histology were evaluated.RESULTS: Ninety‐eight subjects comprising 92 CRC patients and six extracolonic cancer patients from 13 typical and 19 non‐typical HNPCC kindreds were enrolled. There were 53 patients with CRC, one with both CRC and extracolonic cancer and five with extracolonic cancer in the typical HNPCC group, and in the atypical group there were 38 patients with CRC and one with extracolonic cancer. The average onset age of typical HNPCC and atypical HNPCC was 48 and 50 years, respectively, without statistical difference. There were no statistical differences in sex, pathological type, stage, site distribution of the tumor or survival between typical HNPCC and atypical HNPCC groups. There were 11.1% (6/54) metachronous CRC in the typical HNPCC group, and 7.9% (3/38) metachronous and 2.6% (1/38) synchronous CRC in the atypical HNPCC group.CONCLUSION: The Amsterdam criteria are important, but inappropriate for the establishing the clinical diagnosis of HNPCC in Chinese patients, with some atypical families that did not fulfil all the Amsterdam criteria probably possessing similar clinicopathogical features and genetic alterations. It seems that HNPCC should be considered in some suspected cases.