Vanadium (V) solubility in the Al2O3-CaO (25 mass%)-SiO2 system was determined experimentally at 1873 K and at a fixed oxygen potential of 9.37×10-11 bar. EPMA microanalyses were employed to identify the phases and their compositions in the quenched samples. It showed that the solubility of V-oxide increased slightly with decreasing Al2O3-content in the interval from 3 mass% to 53 mass%. The maximum V-solubility was up to 7 mass% (as V). A solid solution rich in V-oxide was detected. The Al2O3 solubility in this solid solution was found to increase with increasing Al2O 3-content in the liquid.