In this study 12 novel benzimidazole compounds bearing hydrazone moiety were synthesized in order to investigate their possible antibacterial and antifungal activity. Structures of the synthesized compounds were elucidated by spectral data. Six different gram-negative and four different gram-positive bacterial strains were used in antibacterial activity tests. Antifungal activity tests were also performed against three different fungal strains. Most of the test compounds found to be significantly effective against Proteus vulgaris, Staphylococcus typhimurium, Klebsiella pneumoniae and Pseudomonas aeruginosa gram-negative bacterial strains. A structure activity relationship (SAR) study including some electronic parameters was carried out and a connection between antibacterial activity and electronic properties of the target compounds was determined. Toxicity of the most effective compounds was established by performing Brine Shrimp lethality assay. (C) 2010 Elsevier Masson SAS. All rights reserved.