The differential thermal analysis (DTA) on BaB2O4 (BBO) single crystals and polycrystalline material has been performed under both oxidising and inert atmospheres. The melt: under oxygen is found to supercool down to 966 degreesC, while under argon the crystallization temperature is further lowered to 887 degreesC. This novel observation has been found to be extremely useful for the growth of beta -BBO crystals by the Czochralski technique. The results obtained have been explained in terms of the melt oxygen stoichiometry.