Oldhamite (CaS) is a key mineral in rare earth element (REE) budget of enstatite chondrite (EC). REE are important for tracing and dating cosmochemical processes, and a precise knowledge of their behavior in the EC formation conditions is essential.We present REEsulphide/silicatepartitioning values (D), obtained at 1300 and 1400°C from experiments performed in evacuated silica tubes for different oxygen fugacityconditions (from IW-6.9 to IW-4.1).Analyses were done on sulphidesand silicates byelectron microprobe for major elements and with Laser Ablation ICPMS for trace elements. ObtainedDvalues are between 0.5 and 5 for oldhamites and between 0.001 and 1 for FeS. These results are in agreement with literature data [1,2]but provide a more complete dataset. We note positive anomalies for Eu and Yb partition coefficientsin both sulphides. Here positive anomalies appear to be caused byEu and Ybreduction to Eu2+and Yb2+.This is confirmed byX-ray Absorption Near Edge Spectroscopy (XANES) analysison Yb. XANES on Sm also shows evidence of some Sm2+in the system.An extensive study of thepartitioningdatahighlights therelation between the intensity of the anomaly and the oxygen fugacity of the experiment.The obtained partition coefficients cannot explain the observed high (100 to 1000 x CI) REE abundances in natural CaSfrom reduced meteorites[3,4]. Hence,the natural REE patterns cannot be explained by CaS crystallization on the liquidus. In primitive EH, positive Eu and Yb anomalies may reflect thepresence of Eu2+and Yb2+in CaS.