A prospective study concerning colorectal polyps in symptomatic patients was held at Lima, Perú, an area considered of low incidence for colorectal neoplasia. In 137 patients, 272 polyps were resected by colonoscopic polypectomy or surgery. 55.9% were adenomas, 40.4% non neoplastic polyps and 3.7% polypoid carcinomas. The distribution of polyps, and the incidence of dysplasia and malignant changes in the adenomas, were similar of that reported in areas with high incidence of colorectal cancer. A high proportion of patients with adenomas (21.4% had a synchronous advanced carcinoma, specially if there were multiple adenomas. The figure was lower in patients with only non neoplastic polyps (7.5%). There were no cases of "de novo" carcinoma. This evidence suggest that adenomas play an essential role in colorectal cancer histogenesis, even in areas of low incidence of this neoplasia.