Viscoelastic properties are followed during the formation of gels by moderately concentrated solutions of atactic polystyrene (aPS) in a mixed solvent of carbon disulfide and tri-m-tolyl phosphate (TCP). This mixture is a thermodynamically "good" solvent for aPS and with solution glass transition temperatures far below the temperatures used in the study. Gel formation is driven by the CS2 component, at temperatures and polymer concentrations similar to those observed in solutions of aPS in pure CS2. The TCP adjusts the viscoelastic response to a convenient range. The results show appreciable hysteresis in the melting and formation temperatures of gels, with the gel formation being a slow process, permitting dynamic mechanical or creep and creep recovery studies as a function of ageing during gel formation, as well as on the solutions prior to permit gel formation. These data reveal systematic behavior analyzed using the linear viscoelastic constitutive relation to obtain the viscosity and a measure of the steady-state recoverable compliance prior to gel formation and the equilibrium compliance after gel formation. This behavior is discussed in terms of models in which segments of the backbone possess a helical conformation stabilized by interactions with CS2 and gel crosslink loci formed via these sequences. (c) 2007 The Society of Rheology.