The bioelectrical response of cultured epithelial cells of normal human sweat gland ducts to isoproterenol was investigated using a modification of the Ussing chamber technique. Evidence of an isoproterenol activation of a chloride ion specific permeability that conducts the chloride ions in a direction governed by their prevailing electrochemcial potential gradient is provided. The short-circuit current remained unchanged during isoproterenol stimulation indicating no effect on active ion transport mechanisms.