The aim of the research: The aim of the research is to examine the potential cytotoxic effects of tieno[2,3-b]piridine derivates on human ovarian cancer cells. Materials and methods: The cytotoxicity of thieno[2,3-b]pyridine compounds, i.e. inhibitors 5, 6, 8 and 9, was tested on the SKOV-3 cell line using the MTT method, based on which the percentage of metabolically active cells is determined. The effect of thieno[2,3-b]pyridine was examined in seven different concentrations after 4, 24, 48 and 72 hours of incubation. The effectiveness of the tested compounds was determined spectrophotometrically at a wavelength of 570 nm. Results: The results are presented graphically in relation to the incubation time and the percentage of metabolically active cells. All tested compounds showed cytotoxic activity dependent on concentration and incubation time. Cytotoxic activity is not in all cases proportional to the increase in inhibitor concentration and incubation time. Inhibitor 6 showed the lowest cytotoxicity. Inhibitor 8 showed the highest cytotoxicity at a concentration of 5 μmol/L after incubation for 72 hours, where the percentage of metabolically active cells decreased to about 40 %. Also, the IC50 values measured for inhibitor 8 were 8.276 μmol/L after 24h incubation, 5.68 μmol/L after 48h, and 4.093 μmol/L after 72h. Conclusion: In vitro exposure of ovarian cancer cells to thieno[2,3-b]pyridine derivatives leads to a decrease in the number of live cells. The cytotoxic effect of the tested compounds depends on the concentration and incubation time. In some cases, the cytotoxic effect is not proportional to the increase in concentration and incubation time because there is a slight increase in metabolically active cells due to cell recovery. The weakest cytotoxic effect was shown by inhibitor 6, and the strongest by inhibitor 8. The obtained results confirmed the hypothesis of this research. Additional in vitro and in vivo animal studies are needed to determine their cytotoxic effect and the potential development of new drugs for the treatment of ovarian cancer.