To investigate whether a selective intercellular communication exists between transformed epithelial cells and their counterparts, the homologous and heterologous communication capacities of four rat liver epithelial cell lines were compared with their expression of transformed phenotypes. All four cell lines showed reasonably good homologous junctional communication capacity, as measured by the dye-transfer assay. In heterologous co-cultures, the non-transformed cell line IAR 20 did not communicate with the transformed cell lines IAR 6-1 or IAR 27 F. These two cell lines showed a high degree of transformed phenotypes such as cell morphology, growth in soft agar and expression of gamma-glutamyltranspeptidase activity. Another cell line IAR 27 E, showed the least degree of transformation and it communicated with IAR 20 cells. Thus, it appears that there is an inverse correlation between the extent of expression of transformed phenotypes by rat liver epithelial cells and their ability to communicate with non-transformed counterparts. There was no heterologous intercellular communication between any combination of IAR 27 E, IAR 27 F and IAR 6-1 cell lines.