Poly(ethylene glycol) (PEG) star polymer hydrogels were prepared by γ-irradiation of aqueoussolutions of star PEG polymers. The swelling behavior of these gels in deionized water at 37 °C indicatedthat the gels prepared from PEG star polymers with a small number of long arms swelled to a greaterextent than those prepared from PEG star polymers with a large number of short arms. PEG starpolymers and branched PEG polymers were modified to incorporate acrylate groups on the ends of thepolymer arms. These acrylated star or branched polymers were copolymerized with poly(ethylene glycol)diacrylate in the presence of UV light. The ensuing materials swelled to a greater extent than hydrogelsprepared without acrylated star or branched PEG polymers. Number-average molecular weights werecalculated using several rubber elasticity-based theories.