Fifty nine cases of colorectal cancer confirmed postoperatively by histologic examination were correlated with the findings of biopsy specimens and cell brushings. Fifty one cases were positive for malignancy on biopsy (86.4 percent). Brush cytology was positive in 51 cases (86.4 percent). The total preoperative confirmed diagnostic rate of the series was 91.5 percent. Brushing cytology under direct vision at fiberoptic colonoscopy, is a safe, reliable, and quite accurate method for the diagnosis of colorectal cancer. The results from brush cytology did not relate to the configuration and appearance of the tumor. For cell brushing, the fluid in the colonic lumen should be aspirated off as throughly as possible. Cell brushings are often positive when colonic stricture and obstruction prevent the colonoscope from reaching the lesion; biopsy, obviously, cannot be done in such a case. © 1987 American Society of Colon and Rectal Surgeons.