The effects of various catalysts on the reactive blending of poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) was investigated. The various catalysts employed for PET syntheses, Ti(OBu)(4), SmL(3), EuL(3), Ca + Sb, CeAc3, Er(NO3)(3) . B12C4, and Tb(acac)(3) . diPy (where L is o-formylphenolate; B12C4 is a crown ether, benzo-12-crown-4; acac is acetylacetonate; and diPy is 2,2’-dipyridyl) have shown a different catalytic activity toward exchange reactions. Solubility tests, in solvents able to separate unreacted PET and PC, and selective degradation of the PC segments, combined with H-1 NMR spectroscopy and size exclusion chromatography, made it possible to order the catalysts according to their catalytic activity : Ti(OBu)(4) much greater than SmL(3) > EuL(3) > Ca + Sb > CeAc3 approximate to Er(NO3)(3) . B12C4 > Tb(Acac)(3) diPy approximate to 0.