The flexibility parameters of chlorosulfonated polyethylene indicate chain stiffness comparable to other synthetic elastomers. Similar conclusion is also reached from a study of the hydrodynamic behavior. The Mark-Houwink constants, obtained from the molecular weight dependence of |η|, also indicate a fairly coiled up configuration for the molecular chain. The parameters characterizing the stiffness of the elastomer chain, such as the effective bond length (b), the steric factor (σ) also reveal that the chlorosulfonated polyethylene chain resembles the other elastomers so far as the chain flexibility is concerned. Unperturbed dimension values obtained from θ-solvent data and other theories of dilute polymer solutions show good agreement with each other.