ndk are a strain of human epidermal keratinocytes that do not undergo terminal differentiation and which grow as single cells rather than compact colonies. We show that ndk are motile and secrete an epithelial scatter factor that has the same biochemical and immunological properties as the scatter factor previously purified from ras-transformed 3T3 fibroblasts. We have found that suramin, a polyanionic detergent, will reverse the activity of scatter factor from either cell type in the standard MDCK activity assay. When added to ndk cultures, suramin causes the cells to grow in coherent patches. This morphological change is accompanied by alterations in the distribution of actin and integrins, but not by stratification or terminal differentiation. The effect is reversed upon removal of suramin. We propose that the motile phenotype of ndk is due, at least in part, to autocrine production of scatter factor and that suramin may be useful for further studies of scatter factor binding to the cell surface.