This prospective study was done in a health maintenance organization colorectal cancer screening program to determine whether 166 persons found to have abnormal fecal occult blood test results typically underwent complete diagnostic evaluation (i.e., either colonoscopy or barium enema x-ray plus flexible sigmoidoscopy). Chart audit data show that 137 (82%) subjects contacted a physician to discuss follow-up. A complete diagnostic evaluation was recommended to only 52 (38%) patients who talked with a physician. Forty-two (81%) patients who were advised to get a complete diagnostic evaluation actually complied. Significant differences in clinical findings were observed for patients who did and did not have a complete diagnostic evaluation.