Phase relations of CuFeO2 during crystal growth under Ar, CO2 and Ar + 0.5% O-2 surrounding atmospheres have been investigated using scanning electron microscopy together with electron probe microanalysis and X-ray powder diffraction. CuFeO2 was found to partially decompose into Fe2O3 and Cu2O before melting and the crystal growth process was by means of Cu2O-solvent movement. Under Ar and CO2 atmospheres, Cu2O was found to be further reduced to metallic copper, and under CO2 more severe reduction of copper was observed. No copper reduction could be found under an Ar+0.5% O-2 surrounding atmosphere.