I. To determine the relative efficacy of celecoxib plus eflornithine (DFMO) versus celecoxib plus DFMO placebo in participants with familial adenomatous polyposis (FAP), as evidenced by the percent change from baseline in the number of polyps in focal area(s) of the colorectum in participants having 5 or more >= 2mm colorectal polyps with or without duodenal polyps at baseline.