Abstract: The addition of selected combinations of aliphatic and aromatic phosphite compounds to polyester or copolyester blends with polycarbonate results in unexpected improvements to the properties of resulting molding compositions. The molding compositions comprise:(a) 10-90% by weight of a polyester or a copolyester, comprising:repeat units from at least one aromatic, aliphatic, or alicyclic dicarboxylic acid, wherein the aromatic portion of said aromatic dicarboxylic acid has 6-20 carbon atoms, and wherein the aliphatic or alicyclic portion of said aliphatic or alicyclic dicarboxylic acid has 3-20 carbon atoms, andrepeat units from at least one aliphatic glycol having 2-20 carbon atoms;(b) 90-10% by weight of an aromatic polycarbonate of 4,4-isopropylidenediphenol (bisphenol-A); and(c) 0.1 to about 2% by weight of a combination of aliphatic and aromatic phosphite compounds.