Alterations in ionic conductance may represent an early mitogenic signal; therefore, impedance analysis was used to examine differences in the electrical properties of the distal colon in a cancer-susceptible (CF1) and a cancer-resistant (DBA) strain of mouse following administration of the carcinogen dimethylhydrazine. The electrical conductance of the surface colonic epithelium increased in CF1 mice from a mean (+/- SEM) of 41.1 +/- 3.0 milliSiemens.cm-2 (mS.cm-2) in controls to 52.6 +/- 3.1 mS.cm-2 following dimethylhydrazine treatment. The conductance decreased in the cancer-resistant DBA group from 154.6 +/- 44.1 mS.cm-2 in controls to 35.1 +/- 17.2 mS.cm-2 following dimethylhydrazine treatment. This difference in response to the carcinogen may partly explain differences in susceptibility noted between these two species. Epithelial impedance analysis may be of use in the early detection of the colon at risk for subsequent cancer development.