Parlodion membranes formed by the dipping technique using solutions of Parlodion in isoamyl acetate of concentrations extending to 3% have been characterized. The thickness of the membrane increased with increase in the viscosity of the membrane-forming solution. Although the membrane resistance increased with increase in its thickness, the specific resistance ρ of the different membranes was not a constant but increased with increase in thickness and showed a tendency to attain a limiting value. The effects of different cations at the same concentration and of the same cation at different concentrations on membrane properties have been studied. Membranes formed by multiple dips into the same solution and into different solutions of Parlodion have also been characterized in respect of their electrical resistance, capacitance, and specific resistance. In general, all Parlodion solutions on a second dip gave membranes of increased thickness and resistance. Subsequent dips always increased membrane thickness and resistance except in the case of 0.25% solution which produced a membrane of approximately the same thickness and resistivity. The dipping and the spreading techniques of membrane formation have been used to introduce stearic acid, phosphatidyl L-serine, and cholesterol into the Parlodion matrix, and the lipoidal membranes so prepared have been characterized.