The transformed or normal phenotype of cultured normal rat kidney cells infected with a temperature-sensitive mutant of avian sarcoma virus is conditional on the temperature at which the cells are grown. Using dye injection techniques, we show that junction-mediated dye transfer is also temperature-sensitive. The extent and rate of transfer between infected cells grown at the transformation-permissive temperature (35°C) is significantly reduced when compared to infected cells grown at the nonpermissive temperature (40.5°C) or uninfected cells grown at either temperature. Infected cells subjected to reciprocal temperature shifts express rapid and reversible alterations of dye transfer capacities, with responses evident by 15 min and completed by 60 min for temperature shifts in either direction. These results suggest that altered junctional capacities may be fundamental to the expression of the ASV-induced, transformed phenotype.