2-Aryl-5-fluoro-6-(4-methyl-1-piperazinyl)benzimidazoles (8a-k) were synthesized for bioassay via interaction of 4-fluoro-5-(4-methyl-1-piperazinyl)-1,2-diaminobenzene with the appropriate aldehyde. The intermediate Schiff bases (7a-k) were isolated and converted, thermally in nitrobenzene, to the respective heterocycles (8a-k). However, none of the tested model compounds (8c-e) showed any significant in vitro activity against Pseudomonas aeruginosa, Staphylococcus aureus, Aspergillus parasiticus and Candida albicans at concentration ≤ 100 μg/ml.