Phenolic copolymers have been prepared with two different feed compositions from some typical phenolic monomers, such as, p-Chlorophenol, p-Cresol and p-Aminophenol. They have been characterized by known methods. Some interpolymer complexes of the phenol ic copolymers have been prepared with polyelectrolytes, such as poly(methacrylic acid) (PMA) and poly(ethylene imine)(PEI). The degree of linkage, stability constant, enthalpy and entropy changes of the systems were determined at several temperatures. Interpretations have been sought in terms of the various interacting forces involved in the complex formation.