The new various metal complexes of 5-benzoyl-4-hydroxy-2-methyl-6-phenyl-2H-pyridazin-3-one were synthesized. All the complexes were evaluated for their antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using microdilution procedure. The Cd(II) and Ni(II) complexes exhibited selective and effective activities against one Gram-positive bacterium (Staplylococcus aureus ATCC 6538), one Gram-negative bacterium (Pseudonionas putida ATCC 12633) and against two yeast (Candida albicans ATCC 27541 and Candida tropicalis 1828) in contrast to poor activity observed other microorganisms. The new synthesized complexes were characterized using IR, H-1-NMR and UV spectral data together with elemental analysis. (c) 2005 Elsevier SAS. All rights reserved.