Boric acid is selectively transported by 1,3-diols from a source aqueous phase into a receiving alkaline aqueous phase through a phase of organic solvent (o-dichlorobenzene), Measurements of the transport rates were made using a U-tube apparatus. The process was adapted to liquid membranes supported on polypropylene films. The factors which influence the stability of the supported liquid membrane are discussed, Assuming that the transport of the neutral 1:1 diol-boric acid complex within the organic phase is diffusion-limited, a model is proposed that realistically represents the fluxes of boric acid as a function of the initial concentrations of boric acid acid diol. The experimental diffusion coefficients were determined and agreed satisfactorily with the calculated values.