The phase diagram of the MoFe system between 800 and 1300 °C has been determined using diffusion couples consisting of the pure metals or their alloys. The boundary concentrations were measured with an electron probe microanalyser. The μ-(Fe7Mo6) phase has a homogeneity range from 57 to 61.5 at.% Fe; above 1250 °C the Fe-rich boundary shifts towards the Mo-rich side. The R-phase is stable above 1200 °C. Its Fe-rich boundary lies at 65 at.% Fe and is vertical, but the Mo-rich one shifts from 65 at.% Fe at 1200 °C to 62 at.% Fe at 1300 °C. The σ-phase is stable above about 1235 °C and contains about 45 at.% Fe. α-Fe can dissolve 17.9 at.% Mo and Mo 8 at.% Fe at 1300 °C.