The glycerol content of grape juices and wines has been determined by gas-chromatographic methods using silyl derivatives. The effect of different storage conditions and yeast cultures on glycerol content has been investigated. Grape juice samples with different starting D-Glucose concentrations have been treated with several additives (HPO₄^2?, S₂O₅^2?, NADH and HSO₃^?). Significant glycerol concentration enhancement has been detected in the case of the addition of NADH (5.14 g/L), however the presence of HSO3? prevented the excessive glycerol formation (1.21 g/L).