To study the nature of the molecular motion of bisphenol A polysulfone (PSF) in the glassy state, the molecular motions of copolycarbonates containing the structures of PSF were investigated. Two copolymers were prepared through the multi-step low temperature solution copolycondensation; one with bisphenol A polycarbonate (PC) trimers linked by sulfone units and the other with polycarbonate trimers linked by ether units. The dynamic mechanical spectra of the copolymers showed single secondary relaxation peaks at around 90 ℃: The strength and position of the peaks were not altered from that of PC. The results indicated that the intramolecular cooperativity observed in the motion of PC be not broken by either sulfone or ether linkage, and that the secondary relaxation motion of PSF be also a cooperative motion. The width of the peaks of the copolymers, however, were smaller than that of PC, which suggested the lesser degrees of intermolecular interactions in the copolymers.