Pairs of electrically coupled glomus cells from rat carotid bodies were impaled with microelectrodes. In the current clamp mode, intracellular stimulation and recording established the coupling coefficient (KC), across the intercellular junctions. About 80% of 26 pairs uncoupled during exposure to 9.45 mM [Ca2+]o, and about 72% of 18 pairs showed the same effect during applications of ionophore A23187. During superfusion with zero [Ca2+]o and EGTA, about 73% of 40 pairs of cells became more tightly coupled. Similar results (71%) were obtained during exposure of 42 cell pairs to BAPTA/AM, a membrane-permeant calcium chelator. Thus, [Ca2+]i seemed to play a significant a role in glomus cell intercellular communication. A23187 and BAPTA/AM, dissolved in DMSO, tended to reduce intercellular coupling during prolonged exposures of the preparations to this solvent. Consequently, the effects elicited by A23187 and BAPTA/AM were superimposed on a coupling effect produced by DMSO.