Perbenzyl derivatives ofd-glucose,d-mannose,d-galactose,d-xylose,d-ribose andl-arabinose were prepared by treatment of reducing sugars with benzyl bromide in DMSO in the presence of potassium hydroxyde and the composition (α/β, Pyranoside/Furanoside) of the reaction mixtures determined by13C-Nuclear Magnetic Resonance spectroscopy. Most of the per-O-benzyl glycosides were obtained in crystalline form unlike the corresponding methyl per-O-benzyl glycosides. Benzylation ofd-mannose gave almost exclusively penta-O-benzyl-β-d-mannopyranoside (≥ 95%) as cristalline material. Benzylated reducing sugars were further obtained in good yield by acid hydrolysis of above compounds.