Objective：To discuss the clinical manifestations of familial adenomatous polyposis （FAP） and summarize our experience in diagnosing and treating the FAP patients. Methods： Clinical data of 96 FAP patients （1985-2003） were reviewed and colonoscopic findings were analyzed retrospectively. Abdominal CT findings and endoscopic findings of the upper digestive tract in 22 FAP patients （2001-2003） were analyzed retrospectively in an attempt to seek extrarectal pathological manifestations in FAP patients. Results.- Densely grown polyps were found in the colorectum in most patients（52/96,54.2%）, while moderateto-high density of polyps were found in the left hemicolon and rectum. Frequency of cancerization was high for rectal adenoma （23/41,56.1%）. Of the 22 FAP patients, 19 （19/22, 86.3%） had proliferative polyps of the gastric antrum and 18 （18/22, 81.8%） had duodenal polyps, including 12 duodenal adenornatous polyps, without a single case of cancerization. In 3 of the 22 FAP patients, desmoid tumors were detected in the abdominal wall, abdominopelvic cavity or mesentery of small intestine 5 years after colectomy. Of the 3 patients, only one was cured by complete resection of the tumor. Conclusion： Dense growth of polyps in the colorectum is a typical clinical manifestation of FAP. Frequency of cancerization is high for rectal adenoma. Colonoscopy is safe and effective for early diagnosis of FAP. Presence of polyps in the upper digestive tract is a common extrarectal manifestation of FAP. Cancerization of duodenal adenoma is rare in Chinese FAP patients. Desmoid tumor significantly influences postoperative quality of life of FAP patients who received prophylactic colectomy