A quantitative study has been made of the intercellular movement of chloride in Chara corallina, using pairs of joined internodal cells. One cell of the pair (cell 1) was exposed to a solution containing 36Cl; the distribution of this tracer between the cells was determined at the end of the uptake period. Of the chloride taken up, 0.29 was transported out of cell 1 for all uptake times from 1.8 to 22 ks and 0.57 was transported to the vacuole of cell 1, in experimental series I. In series II, the fraction transported out of cell 1 was 0.43 at 22 and 43 ks, but 0.17 at 600 s. These results represent a rate of transport of 4 to 60 pmol s−1, across an intercellular wall of area 1.5 × 10−6 m2; the wall has 0.03 to 0.04 of its area occupied by plasmodesmata. The estimate of transport rate is based on an attempt to determine the specific activity of the cytoplasm of cell 1. The electric resistance of the node was found to be 47 mΩ m2. The observed transport rate can be explained by diffusion in the plasmodesmata, without the need to postulate active processes. Diffusion in the plasmodesmata is slower than in free solution by an ‘impediment factor’ of 7 to 700, depending on the assumed chloride concentration of the ground-plasm. If the plasmodesmata offer the major conducting path for electric current, the electric impediment factor is 390. Chloride enters the plasmodesmata from the same small kinetic compartment which supplies the flux to the vacuole, or from a smallintermediate compartment.