The compounds which exist in the system KVO 3V 2O 5 were investigated by melting samples of KVO 3 and V 2O 5 at various mole ratios in a controlled atmosphere furnace. The compounds which formed were identified by X-ray powder diffraction technique. The oxidized compounds KVO 3, K 3V 5O 14, K 2O·4V 2O 5 and V 2O 5 were identified. The compound K 3V 5O 14 has not previously been recognized as a high temperature phase. The reduced oxide V 12O 26 was formed under certain conditions. Two additional phases were present in some samples. One of these may be the vanadylvanadate or vanadium bronze, K 2O·V 2O 4·5V 2O 5. The other was not identified.