Introduction: Benzimidazoles are heterocyclic aromatic organic compounds which, in their composition, contain benzimidazole nuclei, which are used to prepare synthetic compounds of structurally different derivatives. Benzimidazole derivatives show a wide spectrum of biological, pharmacological, and biochemical effects. Some derivatives show potential inhibitory activity of the single-stranded DNA binding molecule activity that can be useful in the treatment of tumour, bacterial, and viral diseases. Objective: The aim of the study is to investigate the effect of benzimidazole derivatives on the cell cycle, to determine the changes in the cell cycle, and to define the substance that has the greatest effect on tumour cell growth. Materials and Methods: For the purposes of the research, the derivatives were prepared at the Faculty of Veterinary Medicine in Zagreb, Department of Chemistry and Biochemistry. The growth of a cell culture in vitro involves culturing cell culture bottles in a CO2 incubator under the conditions of 37 °C with 5 % CO2. The suspension cell lines (Raji and MOLT) are maintained by taking a part of the volume and adding a new RPMI medium. After the treatment of the benzimidazole derivative cells, the cell cycle cell changes were analyzed using flow cytometry. Results: The antiproliferative effect of all the tested derivatives on the cell lines was observed, except for MB-167, which does not affect the cell cycle at any stage. The MB-164 derivative has the strongest effect on the cell cycle. MOLT proved to be more sensitive to the effects of benzimidazole derivatives, compared to the Raji line. Conclusion: Benzimidazole derivatives cause changes in the cell cycle of tumour cells and inhibit their growth depending on the structure of the compound and the type of the cells.