Intrinsic viscosities [η], sedimentation coefficients s, radii of gyration Rg and second virial coefficients A2, refractive index increments and apparent specific volumes were determined in aqueous solution in theta solvents and over a wide range of concentrations ms of a supporting electrolyte KCl, for five samples of potassium polystyrene sulfonate prepared by sulfonation of narrow molecular weight distribution polystyrenes. Coil expansion coefficients α as well as the Flory coefficient Φ relating [η] to coil dimensions were evaluated. Following a theory of Alexandrowicz, α2 was found to be a linear function of M1/4 m−1/3S; Φ appears to decrease with increase in α. The low values of Φ, characteristic for polyelectrolyte solutions, are consistent with the value determined for the Mandelkern‐Flory parameter β = Φ1/3 P−1.