Borowiec K., Szwajgier D., Olejnik A., Kowalska K., Targoński Z. (2016): Effects of a bilberry preparation on selected cell lines of the digestive system. Czech J. Food Sci., 34: 300–305. Bilberry is a valuable wild forest fruit harvested in many countries in Europe. The biological activities of bilberry include antioxidant, anticancer, antiviral, antibacterial, and anticholinesterase activities. This study examines the protective effects of a bilberry (BB) preparation on IEC-6, Caco-2, and HepG2 cell lines. The 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay was used to study the cytotoxicity of BB. The genotoxicity was determined using single-cell microgel electrophoresis. The Ames test was employed to assay bilberry mutagenicity. No significant effects of BB (12.5–100 μg dry mass/ml) were observed on the viability of IEC-6, Caco-2, and HepG2 cells. There were no differences in the percentage of DNA in the comet tail between the cells treated with BB (100 μg dry mass/ml) and the control cells. However, a significant reduction of oxidative DNA damage in the HepG2 cells was found. BB exhibited neither mutagenic nor promutagenic effects. Our results suggest that bilberry can be a potential tool in the prevention of chronic diseases, without any undesired effects on the cells of the gastrointestinal tract.