The interaction of trivalent actinides with aminopolycarboxylate ligands in aqueous solution is reviewed. The strength of complexation to form binary and ternary complexes is interpreted in terms of cationic hydration and structural effects in the interaction of metal cations with aminopolycarboxylate ligands. The trends in the enthalpies and entropies of complexation of actinide and lanthanide cations are compared and discussed in terms of those effects. The results of the spectral measurements, TRLFS, 13 C NMR and EXAFS, provide information on the binding modes and structural aspects of the complexation. These results reflect the progress in recent years in understanding the factors determining the complexation thermodynamics and the structural aspects of the interaction of f-element cations with aminopolycarboxylates ligands.