We investigated the relative effectiveness of four differentiation-inducing chemicals to induce a more normal or benign phenotype in the human colon cancer cell lines Moser and HT29. The differentiation-inducing capability of all-trans retinoic acid (ATRA), difluoromethylornithine (DFMO), sodium butyrate (NaB) and sodium suramin (NaS) was evaluated in terms of the efficacy of these chemicals in inhibiting cellular proliferation, growth in soft agarose, invasion of matrigel and induction of morphological alteration. The relative ability of these chemicals to induce production of the differentiation-related molecules fibronectin and carcinoembryonic antigen was also determined. Overall, ATRA was found to be the most effective chemical in inducing differentiation as measured by these parameters. The Moser cells were more susceptible to differentiation induction by comparison with the HT29 cells. Both similarities and differences in the cellular responses to DFMO, NaB and NaS were also observed for the Moser and HT29 cells. The differences in cellular responses to these chemicals may be due to different phenotypic properties of these two cell lines and different mechanisms of action of these chemicals.