Dilute solution properties of Union Carbide polysulphone have been measured by light scattering, osmometry, and viscometry; Mark-Houwink expressions have been determined in a thermodynamically good solvent, two thermodynamically bad solvents, and one solvent at the θ-temperature. The following relationships have been obtained: [ν] (ml/gm)= 0·145× M ̄W0·50(dimethylsulphoxide, 105·5°)[ν] (ml/gm)= 0·103× M ̄W0·55(dimethylformamide, 25°)[ν] (ml/gm)= 0·079× M ̄W0·58(tetrahydrofuran, 25°)[ν] (ml/gm)= 0·024× M ̄W0·72(chloform, 25°). The values of the unperturbed dimensions, (< ro2 > /M) 1 2 solvent-polymer interaction parameters (B and Xi) and conformational parameter (σ) have been computed by applying the theories of Stock-mayer-Fixman-Burchard, Flory-Fox-Schaefgen, Kurata-Stockmayer-Roig, Ptitsyn and Inagaki-Suzuki-Kurata. Because of uncertainty in the values of the various bond angles in the polymer chain the exact value of σ cannot be given, but it must be close to unity. This low value is not unexpected, it is shared by other polymers containing X-Ph-X links. © 1969.