AbstractPhase transformations associated with spinoidal decompositions are reviewed. Such phenomena associated with inorganic glasses are considered for the case of amorphous binary systems of organic high polymers. The thermodynamic and experimental considerations are projected and sample systems selected and tested. Results are presented for poly 1, 4(2, 6 dimethylphenylene oxide) plus a copolymer of styrene and orthochlorostyrene and also for this plasticized binary system.