Polyacrylamide networks incorporating hybrid crosslinking agents in which amide and ester functional moieties form part of the vinylic structure have a higher degree of porosity than the more conventional systems as evidenced by electrophoresis and overswelling studies. The increase of porosity may be attributed to two mechanisms of network formation; star or non-star type, which are determined by the reactivity of the vinylic groups present within the monomer structure. The experimental results are in good a,agreement with the theoretical predictions.