Comparative studies of the emission of secondary cluster ions in sputtering of the V group metals (V, Nb, Ta) by Au-m(-) (m = 1-9) molecular ions with energies of 6-21 keV have been carried out. For all the metals, a strong non-additive increase in the yield of the secondary ions under cluster bombardment is observed. The non-additivity coefficients K-mm' increase with the raise of the number of atoms n in the sputtered cluster ions reaching the values of 70-150 for K-31 with n = 10-12. The raise in the yield of atomic V+, Nb+, Ta+ ions with quasi-thermal energy has been found with the increase in the number of atoms in the bombarding Au-m(-) ions. (C) 2004 Published by Elsevier B.V.