This paper reports the synthesis and characterization by elemental analysis, molar electrical conductivity, FT-IR and electronic spectra, magnetic proprieties of some new 3d and 4f complex compounds with an active therapeutical ligand, N, N-dimethylbiguanide (metformine), a powerful anti-hyperglycaemic agent, used for the treatment of diabetic patients with non-insulin dependent diabetes mellitus. The complex compounds synthesized in different molar ratio, are highly coloured powders and were isolated in the systems [M 3d(II)(RBig)X2], X = ClO4-, M(II) = Cu, [M(III) 3d(RBig)X(OH2)3]X2, X = ClO4-, M(III)=Cr, Fe, [M 3d(II) (RBig)(OH2)4]X2, X = ClO4-, M(II) = Mn, [M 3d(II)(RBig)(OH2) 4]X2, X = Cl-, M(II) = Co, [M 3d(II)(RBig)(OH2)2X2], X = Cl, M(II) = Ni, [M4f(III)(RBig) (OH2)4X3], X = NO3-, M(III) = Ce, [M4f(III) (RBig)(OH2)4X3], X = NO3-, M(III) = La. The complexes were tested against different Gram positive, Gram negative bacteria strains and fungi species. The results show that all complex compounds present antimicrobial activity compared with ligand, against most of the tested species. Copyright © 2005 CELSIUS.