The predictive value of hyperplastic polyps of the rectosigmoid for neoplastic lesions in the proximal colon is controversial. Some authors who deny predictive value have proposed a protocol which entails initially biopsying rectosigmoid polyps, and only in the case of adenomas then proceeding to total colonoscopy (protocol 1). The diagnostic and economic efficiency of this protocol, and of an alternative which entailed the full exploration of the colon during the initial examination in the case of rectosigmoid polyps (protocol 2), were evaluated by retrospectively simulating their application to 216 patients who had undergone total colonoscopy. A proximal neoplastic pathology was present in 49.5% of patients with rectosigmoid adenoma, 27.3% of patients with distal non neoplastic polyps alone (33.3% if only distal hyperplastic polyps were considered) and 11% of patients with no distal polyps. Protocol 1 gave rise to a higher cost ($ 58,413), not only compared to protocol 2 ($ 50,276), but also compared to total colonoscopy in all patients ($ 57,008); there was also a larger number of patients who eluded diagnosis (29%, against 16% in protocol 2). In terms of cost per lesion detected and of colorectal cancers prevented (on the basis of an evolution to cancer of 5% of adenomas), total colonoscopy for all patients on principle is advantageous compared to either protocol ($ 864 per proximal lesion and $ 7,082 per cancer prevented). Since distal hyperplastic polyps are also predictive of proximal neoplastic pathology, when rectosigmoid polyps are detected it is both indicated and economic to proceed with the exploration of the entire colon during the initial examination. This appears to be a reasonable compromise compared to total colonoscopy on principle, which has higher overall costs. The latter management, however, should not be ruled out, since it has a better diagnostic yield and lower cost per lesion detected and per cancer prevented.