Abstract Studies of the extraction of niobium and tantalum oxalato solutions with tri-n-octylamine (TOA), tri-n-decylamine (TDA) and tri-n-dodecylamine (TDDA) in carbon tetrachloride have been carried out. The metal/amine ratio was determined in the organic phase and an identical behaviour was observed for all the three extractants. Further studies were carried out in detail with TOA, and extraction-species were separated under different conditions. The infrared spectra of the organic phases were examined and compared with the spectra of the isolated substances. On the basis of this evidence, the mechanism of extraction of niobium and tantalum oxalato complexes with long-chain tertiary amines, is given.