Abstract
1 . The ion distribution in the vas deferens of the guinea-pig was determined following reserpine treatment and decentralization, procedures known to increase the sensitivity of this muscle to drug stimulation. 2 . There were no significant changes in the estimated intracellular ion concentrations following the two procedures. The half-times of 42K and 36C1 effluxes were also unaltered. 3 . As far as ion content is concerned there is no basis for suggesting an altered resting membrane potential in supersensitive smooth muscle.