The effect of phase equilibrium and microstructure of magnesite-chromite batches containing from 0 to 100% Egyptian chrome ore, with intervals of 10%, on their physical properties was studied. The phase equilibrium data were calculated using the phase relationships within the system M-M(2)S-CMS-MR (M = MgO, S = SiO2, C = CaO, R = R(2)O(3)) A computerized electron-probe microanalyser was applied to study the microstructure as well as microchemistry of the fired magnesite-chromite co-clinkers. Some physical and technological properties of the co-clinkered briquettes were also investigated by determining densification parameters, spalling resistance and load-bearing capacity. It is concluded that dense, spalling resistant and refractory magnesite, magnesite-chrome and chrome-magnesite refractories could be produced by co-clinkering of magnesite-chromite batches of 100:0, 70:30 and 30:70 weight ratios, respectively, at 1600 degrees C. The prepared co-clinkers were subsequently graded, moulded and refired up to 1700 degrees C in order to obtain direct-bonded bricks. Meanwhile, dense chromite refractories with lower refractory quality could be processed by firing the Egyptian chrome ore up to 1600 degrees C.