Condensation of o-phenylenediamine with formic acid, acetic acid and glycolic acid gave a series of benzimidazole which on reaction with alkyl halide in phase transfer catalysis afforded the formation of the corresponding 1,3-dialkylbenzimidazolium salts. The structure has been established on the basis of spectroscopic and spectrometric analysis (1H and 13C NMR, IR, MS and single X-ray diffraction). The in vitro antibacterial activities of these salts have been investigated.