While clonal cell variants of BALB/c 3T3 with high and low susceptibilities to ultraviolet radiation- and benzo(a)pyrene-induced transformation show similar intercellular communication capacities when they are in the growing phase, a significant loss in communication occurs at confluence only in transformation-sensitive clonal variant cells. A potent tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, which also enhances BALB/c 3T3 cell transformation induced by methylcholanthrene, inhibited intercellular communication of these variants to a similar extent. These results suggest that intrinsic differences in the control of intercellular communication may be a determinant of the susceptibility of these variants to the induction of transformation.