The reactive sintering of Ti/Al4C3/C mixtures at a temperature of 1417 degrees +/- 5 degrees C to form the ternary carbide Ti3AlC2 was studied in situ by neutron powder diffraction. A series of intermediate phases occur during the synthesis process beginning with the formation of beta-Ti, TiCx (x <= 1) and Ti3AlC. This is followed by the transition of Ti3AlC to Ti2AlC, after which the Ti2AlC and TiCx react with each other to form the product phase Ti3AlC2.