The removal or elimination of organic residues from aqueous waste streams represents a major need in the chemical industry. We have developed a class of membrane called supported polymeric liquid membranes (SPLMs) capable of removing and concentrating low molecular weight organic compounds from dilute aqueous solutions, especially those that also contain high levels of inorganic salts. The membranes are prepared by filling the pores of microfiltration or ultrafiltration membranes with functional, polymeric (oligomeric) liquids having affinity for the organic compounds of interest. Data obtained with para-nitrophenol (PNP) as the permeating organic and polyglycols as the polymeric liquid membranes show that the slow diffusion rates due to the viscous polymeric liquids are more than compensated for by the very high solubility resulting from specific interactions and high density of the polymers functional groups. This is a powerful concept that can be extended to other types of polymeric liquids. Quite interestingly, the transport rates of PNP through the supported polyglycol liquid membranes appear remarkably insensitive to the molecular weight and the viscosity of the polymeric liquids. This behavior may signal a more complex and very different transport mechanism than the usual liquid diffusion.