One hundred ninety-three asymptomatic women with a personal history of breast cancer underwent screening colonoscopy. One hundred sixty-eight women had breast cancer as their only potential risk factor for colonic neoplasia, and 25 had a family history of colorectal neoplasia in addition to their personal history of breast cancer. Among women with breast cancer, increasing age and body weight were each predictive of an increasing prevalence of colonic adenomas. The prevalence of colonic adenomas in women aged 50-75 yr whose only potential risk factor was breast cancer was 18%, and was identical to the prevalence of colonic adenomas in 186 asymptomatic average-risk control women aged 50-75 yr (odds ratio 1.0, 95% CI 0.54-1.87). We conclude that a personal history of breast cancer does not predict a higher prevalence of colonic adenomas.