Acrylamide and poly(ethylene glycol) macromonomer copolymers, in conjunction with phenolic formaldehyde resin (PFR), were evaluated as novel retention aids for newsprint pulps. The first-pass retention of the pulp fines was increased from 37% without polymer to nearly 90% with copolymer addition. This retention performance was similar to that of the high molercular weight polyiethylene oxide) (PEO)/phenolic resin dual-polymer systems. However, the copolymers exhibited improved aging resistance and produced a higher fines retention than PEO (MW = 8 million) under high shear stress.The retention performance of the copolymers was very sensitive to the molecular weight. A new retention mechanism called complex bridging was proposed to explain the retention effects.