The described labelling and purification preparation of N-isopropyl-p-131I-amphetamine /131I-IMP/ represents a fast and efficient method to obtain a compound that fulfils all criteria of purity for its in-vivo application. After isotope exchange and quality control131I-IMP could be obtained with radiochemical yields in the range between 68% and 78% with a radiochemical purity of 98–99%. As demonstrated in animal experiments the cerebral affinity of IMP offers a possibility for the diagnosis of brain diseases in clinical studies when the product is labelled with123I.