Small bowel resection was performed in one parabiont of a parabiotic rat pair to determine whether there was a "humoral" or other circulating factor present which could influence the compensatory response seen in the remainder of the small bowel. Following intestinal resection in one parabiont, there was an increase in DNA synthesis in the intestine of that member provided at least 40% of the small intestine was removed. The compensatory response seen in a resected animal was not observed in its parabiotic partner, even though an attempt was made to make the potentially responding animal more sensitive to the influence of any circulating "factors" by resecting its intestine as well. The results obtained are in disagreement with the one closely related report in the literature; it is suggested that there is no good evidence for the existence of a resection-induced circulating factor with the capability of crossing a vascular anastomosis and controlling proliferation of small intestinal epithelium.