The mixed-ligand complexes of platinum(II) [Pt(Gly)(uracil)Cl2].H2O and [Pt(His)(adenine)]-Cl.2H2O eliminated multicopy plasmids with the ColE1 origin of replication in Escherichia coli with 100% frequency. However, plasmids of the IncF1, H1 and X groups were totally refractory to these agents under similar conditions.