A method for the preparation of [1-11C]D-glucose (III) and [1-11C] D-mannose (IV) from [11C] nitromethane is described. [11C]Nitromethane was produced using the on-line method from [11C]methyl iodide. The condensation of no-carrier-added or carrier-added [11C]nitromethane with D-arabinose to form the intermediate epimeric [1-11C]D-nitro alcohols (I and II) was investigated under various conditions. Compounds I and II were converted to III and IV by the classical Nef reaction with IV as the major product [(IV)/(III) = 3/1-4/1]. The isolated radiochemical yield of III and IV was 25-30% (based on [11C]nitromethane and decay-corrected) and 14-17% (EOB) with a total synthesis time of 50 min, including HPLC-purification. Compounds III and IV were isolated using semi-preparative HPLC and the radiochemical purity was greater than 97%. In a typical run, 1.5-2.0 mCi of III and 6-8 mCi of IV could be isolated (starting from 70-90 mCi [11C]nitromethane).