The on-line synthesis of 1-11C-labelled nitroalkanes [nitromethane (I), nitroethane (II) and nitropropane (III)], from their corresponding 1-11C-labelled alkyl iodides, by use of a heated silver nitrite column is described. The radiochemical yields of I, II and III were of the order of 40-70%, based on the corresponding [1-11C]alkyl iodides. The total radiochemical yields, starting from [11C]carbon dioxide, were of the order of 25-55% with an overall synthesis time of 8-15 min.