Abstract: Supported anisotropic reverse osmosis membrane based on synthetic polyamides are prepared by first preparing a support therefor for treating a material suited for serving as a support for a polyamide membrane, with a heat resistant water soluble polymer which is insoluble in the polar solvents to be used for preparing the polyamide solution described below; preparing a solution of the polyamide in an organic polar solvent, in the presence of a saline compound; spreading the thus prepared polyamide solution onto the prepared support; partially evaporating the solvent by heating; coagulating the membrane in an aqueous medium; and optionally, thermally treating the membrane.