We analyzed DNA damage, mitotic activity and polyploidization in Crepis capillaris callus cells during short- and long-term in vitro culture, and the influence of plant growth regulators on these processes. Changes in the concentration of growth regulators altered the stability of callus. The level of DNA damage was highly dependent on the growth regulator composition of the medium. Cytokinin at high concentrations damaged DNA in the absence of auxin. Short- and long-term callus differed in sensitivity to growth regulators. Mitotic activity changed when callus was transferred to medium with modified growth regulators. Callus cell nuclear DNA content increased with age and in response to plant growth regulators. Hormones played a role in the genetic changes in C. capillaris callus culture. We demonstrated the usefulness of C. capillaris callus culture as a model for analyzing the effect of culture conditions, including plant growth regulators, on genetic stability.