Because the omentum collects and disseminates cancer cells, omentectomy is an integral part of ovarian cancer surgery. We postulate that the omentum serves a similar function in colon cancer and may contribute to post-operative malignant small bowel obstruction (S.B.O.) and that routine omentectomy during colectomy would reduce the incidence of S.B.O. Fischer 344 rats and a transplantable carcinogen-induced rat colon cancer were used to test: (1) whether the omentum is a unique site of intra-abdominal colon tumor implantation which contributes to S.B.O.; and (2) whether omentectomy at the time of tumor implantation would reduce the incidence of S.B.O. Statistical analysis confirmed that animals undergoing omentectomy had a significantly lower incidence of omental tumors and malignant S.B.O. (26 per cent and 16 per cent respectively) when compared with sham operated animals (75 per cent and 85 per cent respectively, P less than 0.001). These data suggest that the omentum is a source of bowel obstruction from implantation and growth of tumour cells in the rat model. Although this could be tested in other animal systems, the addition of routine omentectomy to colectomy is simple, not time-consuming, and may reduce postoperative morbidity.