A metastable NaCl-structure Cr carbide was formed by 50 keV carbon-ion implantation into pure chromium metal films. The structure of the carbide phase was identified by selected-area electron diffraction to be face-centred cubic (FCC) with a lattice constant of 0.403 nm. The carbide phase was stable only up to temperature of about 250 degrees C and was destabilized at higher temperature, probably because of oxidation. The formation of Cr carbide was also confirmed by Auger spectroscopy measurements. The heat of formation of the phase was calculated to be less negative than those for Ti and V carbides, i.e. -7 kcal mol^-1, which reflected to some extent the metastability of the carbide formed.