Hydrophobically associating water-soluble polymers are essentially hydrophilic polymer chains containing a small number of strongly hydrophobic groups, distributed or located at some priviledged sites on the chains. In aqueous media, hydrophobic units tend to associate in order to minimize their exposure to water, leading to reversible intra- and intermolecular hydrophobic junction networks, at even very low polymer concentrations. Such temporary networks influence strongly the linear and nonlinear rheological properties of the solutions and make such polymers candidates as rheology modifiers in aqueous-based formulations such as drilling fluids. In this paper, we present the main rheological characteristics of hydrophobically associating water-soluble polymers, the influence of the presence of a surfactant on their rheological properties and the rheology of solutions containing a mixture of associating and non-associating water-soluble polymers.