Abstract: Objective 　To evaluate the long2term effect of sulindac in attempting to maintain the regression of colorectal adenomas and changing of pathology of familial adenomatous polyposis ( FAP) patient s. Methods 　FAP patient s who were diagnosed by family history and colonscopy were t reated with sulindac 400mg per day. The patient s received colonoscopy examination regularly to assess number of polyps. Bi2 opsies of remnant polyp s were obtained. The type and dysplasia grade of biopsies were evaluated and compared with baseline. Results 　Eighteen patient s of FAP received sulindac. The average age was (37. 4 ±9. 8) years old. The average period of t reatment was (65. 3 ±31. 6) months. Compared with baseline, the average number of polyp s reduced significantly at last follow2up ( P < 0. 01) . There were totally 200 adenoma biopsies obtained before the t reatment . Among them, 86. 5 % were tubular, while 13. 0 % were tubulovillous adenoma and 0. 5 % was villous adenoma. The dysplasia of grade Ⅰ, Ⅱ and Ⅲ were 40. 0 %, 43. 5 % and 11. 5 %, respectively. Af ter sulindac t reatment, there were totaly 133 adenoma bi2 opsies obtained. 97. 7 % of adenoma biopsies were tubular adenoma, while 2. 3 % were tubulovillous ade2 noma. There was significant difference compared with baseline ( P < 0. 01) . The dysplasia of grade Ⅰ, Ⅱand Ⅲwere 48. 9 %, 48. 1 % and 3. 0 % respectively, which had significant difference with baseline ( P < 0. 01) . However, 1 patient who took sulindac 100 mg/ d by himself developed colonic cancer. Conclu2 sion 　Long2term use of sulindac seems to be effective in maintaining the regression of colorectal adenoma of FAP patient s and reducing dysplasia grade and tubulovillous adenoma of retained colorectal adenoma. These effect s are associated with dosage. However, the effect of sulindac to regress the adenoma seems to be uncompleted. FAP patient s who take sulindac need to receive colonoscopy regularly to find colorec2 tal cancer.