Intestinal folds of adult Xenopus laevis are formed by the proliferation of groups of cells in the tadpole epithelium at metamorphosis. As the folds increase in number and in height, mitoses become confined to the troughs and a gradient of decreasing mitotic activity from troughs to crests is formed. This pattern of cell proliferation was confirmed in autoradiographic studies with [3H]thymidine. Migration of cells from the fold troughs to the fold crests was also demonstrated by thymidine autoradiography and the epithelium renewal time was approximately 16 days. Thus cell proliferation and cell specialisation in the small intestinal epithelium of adult X. laevis are inversely correlated.