Three symmetrical and two unsymmetrical N2O2 Schiff bases obtained from the condensation of o-phenylenediamine with various salicylaldehydes namely salicylaldehyde, 5-nitrosalicylaldehyde and 5-bromosalicylaldehyde were synthesized and characterized based on elemental analysis, IR, 1H NMR and electronic absorption spectroscopy. The antimicrobial activity of the compounds tested against the microorganisms E. coli (ATCC 25922), E. feacalis (ATCC 29212) and S. aureus (ATCC 25923) using the agar ditch method showed a dependence on the substituent present in order H>NO2>Br. The unsymmetrical compounds exhibited higher activity compared to the symmetrical compounds.