Even on consistent use of production-oriented environmental protection measures it still proves impossible to avoid the formation of solvent-containing gaseous effluents in many production processes. Thus the reduction of emissions by purification of solvent-containing process and exhaust gas streams is still a highly topical matter. Thermal, catalytic, or biological oxidation processes leading to destruction of the organic solvents should only be used when solvent recovery is impossible. Preference should always be given to those processes which protect resources by permitting recovery of solvent. Substantial advances in the area of membrane technology during the past ten years mean that gas permeation now constitutes an interesting alternative to conventional processes. Combination of a membrane separation stage with direct or indirect condensation gives a hybrid process permitting gentle and contamination-free recovery of organic components, This article briefly summarises the fundamentals of permeation of gas/vapour mixtures through polymer membranes.