Of one hundred and twenty-six patients with Gardner's syndrome, 60% showed soft tissue tumors, 32% showed osteomatosis, 67% polyposis, and 20% the complete triad. Bowel cancer developed in 32% of the patients. The frequency of other diseases in these patients showed fibrous tumors in 8%, and two patients with cancer of the ampulla of Vater; otherwise the diseases seen did not show any major variation from what might be expected for the group at risk. Laboratory evaluation has included the demonstration of increased fecal cholesterol and primary bile acids in these patients. The recommended surgical treatment is colectomy and ileorectal anastomosis at a measured 12 cm level. This level of ileorectal anastomosis may be vital in giving a regression of rectal polyps, which was seen in 15 to 17 patients so treated. The conversion of an ileosigmoid to an ileorectal anastomosis resulted in polyp regression in one patient. The oral administration of ascorbic acid gave polyp regression in seven of 10 patients. There may be a possible relationship of fecal coprostanol and cholesterol levels and polyp regression.