The phase relationship in the Fe-Pt-Pr ternary system at 500 degrees C was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) energy dispersion spectroscopy techniques. The 500 degrees C isothermal section consists of 13 single-phase regions, 23 two-phase regions and 11 three-phase regions. At 500 degrees C, the maximum solid solubility of Pt in alpha-Fe is about 10 at.% and Fe in Pt is about 18 at.%; the maximum solubilities of Pr in alpha-(Fe,Pt), Fe3Pt, FePt, FePt3 and (Pt,Fe) (the solid solution of Fe in Pt) are about 6 at.% 1.5 at.% 2 at.%, 2.5 at.% and 1.5 at.%, respectively. No Pr3Pt4 binary compound and new ternary compounds were found. (c) 2006 Springer Science + Business Media, Inc.