The effect of ten aliphatic halogenated hydrocarbons was examined in addition to halothane (151677) on intercellular communication in cultured heart cells harvested from 2 to 4 day old Sprague-Dawley- rats. The other ten compounds tested included methylene-chloride (75092), 1,2-dichloroethane (107062), 1,1,2-trichloroethane (79005), chloroform (67663), trichloroethylene (79016), 1,1,1-trichloroethane (71556), carbon-tetrachloride (56235), tetrachloroethylene (127184), 1,1,1,2-tetrachloroethane (630206), and pentachloroethane (76017). Myocytes were suffused with increasing concentrations of halocarbon added as a 0.2% solution of dimethyl-sulfoxide to M199 containing 1.8 millimolar calcium and 5% serum. Single cells were microinjected with the fluorescent probe Lucifer-yellow and dye coupling to adjacent cells was monitored. The findings demonstrated the inhibition of the intercellular communication in cultured heart cells by each of the 11 halogenated hydrocarbons. The immediate and completely reversible action of these chemicals on gap junctional communication paralleled their ability to sensitize the myocardium to catecholamine induced arrhythmias. The inhibition of the intercellular communication appeared to be largely dependent on the ability of these compounds to partition in the cell membrane. These findings supported the theory that the physicochemical properties of the halocarbons are a major factor in their acute effect on the heart.