The effect of doxorubicin on the expression of cofilin and actin in CHO AA8 cells was estimated by fluorescence and electron microscopy. The presence of cofilin and actin was observed particularly in the nuclei of cells by different modes after treatment by doxorubicin. Cells undergoing mitotic catastrophe expressed some entirely characteristic features together with overlapping elements of other types of cell death. Additionally, the authors suggest that, as defined here, reorganization of F-actin might be involved in all cell death processes. Changes in the nuclear expression of cofilin are related to F-actin cytoplasm-nuclear translocation and its intranuclear dynamic reorganization.