Chloride secretion in primary cultures of cells originating from the secretory coil of human sweat glands was investigated by electron probe X-ray microanalysis. The total intracellular Cl concentration was lowered by muscarinic agonists (carbachol and acetylcholine), as well as by the calcium ionophore A23187. The muscarinic agonists also lowered the cellular K concentration. Cl secretion induced by these agonists could be inhibited by the chloride channel blocker NPPB. After cAMP stimulation, the frequency distribution of the Cl concentration changed from Gaussian to bimodal, indicating that cAMP induces Cl secretion only from a subpopulation of the cells. Also ATP stimulated Cl secretion, indicating the presence of purinergic receptors. The results suggest that some of the cells in addition to Ca2+ -regulated Cl channels also possess cAMP-activated Cl channels. Hence, the primary cultures still possess the Cl transport mechanisms known to be present in intact glands. It can, however, not be excluded that some coil cells have acquired ductal characteristics during culture.