Hepatocyte growth factor (HGF), also known as scatter factor, regulates both cell motility and the growth of some cell types. We have determined the effects of HGF on the motility and growth of human colon cancer cell lines (HT115, HT29, HRT18 and HT55). Cell motility, as measured by dissociation from carrier beads or by scattering of cell colonies, was greatly increased in all cell lines. The effects were completely blocked by anti-HGF antibody. In contrast, cell growth of HT115, HT29 and HRT18 cells was inhibited by a wide range of concentrations of HGF. HT55 cell growth was also inhibited but needed a prolonged culture period (> 5 days). The HGF receptor/Met protein is highly expressed in the membrane fraction of these cells as determined by Western blotting. It is concluded that HGF has an effect on both colon cancer cell motility and growth, which may be important in the control of the spread of colon cancer.