Partitioning of sulfur (S), oxygen (O) and silicon (Si) between liquid Fe-Ni-alloy (LA) and liquid silicate (LS) was studied with a multi-anvil apparatus at pressures between 2 and 25 GPa and temperatures between 2073 and 2623 K. We found that S has a strong affinity for liquid Fe-Ni-alloy at all the experimental conditions investigated. Partition coefficient of S between liquid Fe-Ni-alloy and liquid silicate (DSLA/LS) increases with pressure and decreases with temperature. At the proposed pressure and temperature of core-mantle equilibrium during early Earth differentiation [Li and Agee, 1996; Righter et al., 1997>, S is highly siderophile (DSLA/LS~1000), while Si and O are highly lithophile (DSiLA/LS,DOLA/LS<0.03). Our study suggests that if the core composition was largely established by equilibrium partitioning in a deep magma ocean, then S is the most plausible principle light element in the core. ¿ 2001 American Geophysical Union