An original system was developed to detect intercellular communication between epithelial cells of rat colon mucosa. Cell-to-cell communication was tested both in normal and in azoxymethane (AOM)-induced aberrant crypts in an attempt to identify chemically-induced modifications of cell properties. Stripes of unstained live tissue were superfused and oxygenated at room temperature and single cells at the top of the crypt were injected with fluorescent dyes. The bottom cells were filled in isolated crypts. Dyes injected into cells at the surface of the mucosa failed to diffuse to adjacent ones, whereas cells at the base of the crypts were dye-coupled. Surface cells from aberrant crypt foci (ACF) did not transfer the dye, therefore behaving like normal crypts. These results indicate that the pattern of intercellular communication between colon crypt cells changes as these cells differentiate and migrate to the top of the crypts and that the pattern of dye transfer between surface cells is maintained in ACF.