In order to study the influence of glucose and urea on the 1 2 5 I transport across an anion exchange paper membrane, the transmembrane potential, the fluxes, and the concentrations of 1 2 5 I, glucose and urea within the membrane were measured in the Na 1 2 5 I concentration-cell system containing glucose or urea. Glucose and urea increased the membrane/solution distribution of the iodide ion, but scarcely affected the diffusion process of iodide ion within the membrane.