This study was undertaken to assess the reliability of the endoscopic biopsies in the evaluation of colorectal villous tumors (CRVT). In 163 consecutive patients referred for surgical treatment of CRVT, preoperative evaluation had been routinely done by colonoscopy and multiple biopsies. Tumors were classified in 3 groups: low grade tumors, high grade tumors and adenocarcinomas. Infiltration in depth was staged on the postoperative specimens according to the Dukes-Aster-Coller's classification. All the tumors were completely resected by surgery and definitive pathological diagnosis was established. An exact correlation between the pre- and postoperative staging was observed in 48% of the cases. Accuracy averaged 54% in the group-by-group comparison, with an overstaging rate of 6.7%, and an understaging rate of 39%. The incidence of adenocarcinomas was 22% in the group with clearly benign preoperative biopsies and 50% in the other cases. There were significantly more B2 and C tumors among the patients referred after 3 or more endoscopic attempts (33%) than after one or two sessions (10%) (p < 0.0003). We confirm that in spite of multiple endoscopic biopsies, only a complete resection permits an exact staging and an appropriate therapeutic choice.