In this study we report the synthesis and preliminary evaluation of a series of six 2-aryl-5(6)-nitro-1H-benzimidazole derivatives (1-6) as potential anticancer agents. Cytotoxicity was evaluated against seven human neoplastic cell lines using the MTT assay. Compound 6 [2-(4-chloro-3-nitrophenyl)-5(6)-nitro-1H-benzimidazole] was the most active of the series, showing an $IC_{50}$ of 28 nM against the A549 cell line. This compound displayed a selective in vitro cytotoxic activity index (>700) in non neoplastic HACAT cells ($IC_{50}=22.2{mu}M$). Compounds 3 and 6 induce arrest in the S phase of the cell cycle, and compounds 1-6 induce apoptosis in the K562 cell line. Compound 6 induces poly (ADP-ribose) polymerase (PARP) inhibition activity as a potential mechanism of action. These results suggest that compound 6 could be a potent anticancer agent. Compound 3 displayed the best inhibitory activity against PARP with an $IC_{50}$ value of $0.05{mu}M$, compared to the activity shown by the positive control 3-aminobenzamide ($IC_{50}=28.5{mu}M$).