An amido-containing resin which comprises an aminolysis reaction product ofA. a reaction product of (a) a benzene compound and (b) an alicyclic compound, andB. an amino-containing compound, said aminolysis reaction product containing one amido group and one carboxylate group in the molecule; compositions containing the above amido-containing resin which are particularly useful for sizing agent and emulsifier for producing synthetic rubbers by emulsion polymerization.