Stiff, viscoelastic hydrogels have been fabricated from hydrophobically modified poly(acrylamide-co-sodium acrylate) (HRAM). These materials are macroscopically homogeneous but microscopically heterogeneous, containing hydrophobic aggregates that bridge polymer chains in a three-dimensional network. The charge level at which the dynamic storage modulus is maximized for a given polymer concentration corresponds closely with the charge level giving a maximum in hydrophobicity of the aggregates, suggesting a link between the mechanical stability of these aggregates and their ability to exclude water effectively. The gel point, where the system first exhibits viscoelastic behavior, may also be identified from discontinuities in the hydrophobicity (as measured by the fluorescence spectra of solubilized pyrene) and equivalent conductivity with polymer concentration. The effects of various aspects of polymer architecture on hydrogel properties have been investigated. The dynamic storage modulus of the network exhibits a maximum with backbone charge at constant polymer concentration, with a charge level in the range 3.58-4.81 mol % Na acrylate producing the stiffest gels in C-8-substituted HRAMs. An increase of two methylene units in the length of the side chains results in up to 1 order of magnitude increase in the dynamic storage modulus of the gels at constant polymer molecular weight. The anionic surfactant sodium dodecyl sulfate (SDS) exhibits a synergistic effect on gel formation by promoting the formation of intermolecular hydrophobic aggregates despite the presence of negatively charged groups on the backbone. In contrast, the effect of sodium chloride on gel properties is not as pronounced. A literature review on the effects of polymer architecture on the macroscopic phase behavior of hydrogel-forming hydrophobically modified water-soluble polymers is presented.