A process for making a copolymeric resin is disclosed. Accordingly, component (a) and component (b) are introduced into an extruder under conditions designed to promote reactive blending therebetween in the presence of a transesterification catalyst. Component (a) is a wet aromatic polycarbonate resin containing moisture in an amount greater than 0.02 weight percent and having units conforming to ##STR1## wherein D is a divalent residue of a dihydroxy compound. Component (b) is a lactone-siloxane block copolymer having structural units conforming to ##STR2## wherein m is 1-90, n is 60-150, R is an alkyl or a phenyl radical, p is 2-12 and q is 2-20. Surprisingly, use of moisture-containing polycarbonate in the process yields a copolymer having good properties, although a corresponding process where the lactone-siloxane block copolymer reactant has a smaller number of repeating units yields inferior product.