New experimental results on the liquid + graphite + M7C3 equilibrium are presented. The solubility of Co in the M7C3 carbide has been measured at 1523 and 1723 K. These measurements together with recently published measurements on the fcc + graphite + M7C3 equilibrium show that the solubility of Co in the M7C3 is much higher than predicted from thermodynamic calculations. A new thermodynamic description of the Co-Cr -C system is presented which accurately describes the solubility of Co in the M7C3 carbide in the temperature range 1373 - 1723 K.