Eight hundred and twenty patients were examined by fiberoptic sigmoidoscopy (SIG) and double contrast barium enema (DCBE) to detect colonic cancers or adenomas. Cancer or adenoma in the bowel tract proximal to the upper limit of SIG insertion was detected in 4 patients and in 12 on DCBE. The DCBE detection rate of proximal colonic lesions varied according to the hemoccult (HO) outcome. This was 1.16% for cancer and 2.03% for adenoma in HO+ patients and null for cancer and 1.23% for adenoma in HO- patients. The detection rate of proximal adenomas was higher in patients who presented adenomas on endoscopy in the distal bowel (SIG+), 2.46% as compared to 0.48% in SIG- patients, independent of the HO reports. Routine DCBE is practically useless in HO-SIG- patients and questionable in HO-SIG+ patients since improvement of the detection rate is null for cancer and moderate for adenoma. It is recommended for HO+ patients because it increases the colonic cancer detection rate (10.5% in this study).