In this work three radiochemical procedures are presented for the determination of 99Tc in aqueous environmental samples by ICP-MS. Technetium is pre-concentrated from a dilute solution by a reduction-precipitation process using FeSO4 as the reducing agent. The precipitate is treated to extract and isolate Tc by three alternative methods which combine ionic exchange, with conventional or TEVA resins, and solvent extraction techniques using TBP. Special emphasis is paid to isolating the technetium from Mo and Ru, which are the major interfering elements for the mass spectrometric determination of 99Tc.