Abstract A steroid sulphotransferase (EC 126.96.36.199) was partially purified from female rat liver. The enzyme was active towards the substrates, dehydroepiandrosterone, epiandrosterone and pregnenolone but was inactive towards oestrogens, cholesterol and ergocalciferol. A pH optimum of 5.0 was recorded but the enzyme was unstable at low pH. The enzyme was stimulated slightly by the addition of reducing agents and inhibited by p- chloromercuribenzoate and HgCl 2. Crude enzyme activity was markedly stimulated by divalent cations but this effect was not observed with purified enzyme. A K m of 13 μM was calculated for the donor substrate 3′-phosphoadenylyl sulphate and the acceptor substrate, dehydroepiandrosterone had a K m value of 6 μM. The enzyme appeared to be highly susceptible to product inhibition by adenosine 3′,5′diphosphate.