The extraction of the bisulphate and sulphate ions by tetraalkylammonium thiocyanate into an non-aqueous solvent was investigated and the results compared with values from the literature. It is shown that graphical methods for obtaining these extraction constants cannot be justified in this case and thus do not give conclusive results. Least-square methods, without the approximations involved in the graphical methods, had to be employed to obtain more meaningful results. These confirm that both bisulphate and sulphate extract to a significant extent.