A family cancer screening clinic was set up to screen and counsel subj
ects at above average risk of developing colorectal cancer. Criteria f
or referral were one first degree relative under 50 years or two of an
y age with colorectal cancer. Pedigree information was used to estimat
e lifetime risks of developing colorectal cancer and offer appropriate
screening: colonoscopy for high risks (greater than 1 in 10), faecal
occult blood testing for lower risks. One hundred and eleven subjects
from 76 families were seen over four years. Forty two families gave a
pedigree consistent with dominantly inherited non-polyposis colorectal
cancer syndrome (HNPCC). Three subjects from one family were found to
have familial adenomatous polyposis. Ninety two colonoscopies yielded
21 patients with polyps (12 had tubular adenomas, including one with
early malignant invasion). Thirty three per cent (four of 12) of the t
ubular adenomas were beyond the reach of a flexible sigmoidoscope. Thr
ee hundred and forty two further high risk relatives were identified f
rom the family history.