Both (R) and (S)-2,3-dibromo-1-propanol with e.e. up to 60% have been obtained by diastereoselective addition of Br 2 to allyl glucosides and galactosides having only one unprotected hydroxyl group at C-2 or C-6 using tetrabutylammonium tribromide, followed by hydrolysis. The absolute configuration is shown to depend on the position of the free hydroxyl and on the configuration at the anomeric centre.