Cytoskeletons are supposed to play important roles in the cell growth, metastasis and invasion as well as the reduction of the adhesion to the matrix, which are characteristic of cancer cells. The dynamic changes of cytoskeletons were observed during the differentiation of mouse myelomonocytic leukemic cells, M1. We discuss an increase of the vimentin expression, which is correlated with the changes in the cell morphology, and a reduction of the vimentin degradation activity during the differentiation of M1 cells. And we also discuss about an increase of alpha-actinin synthesis, which is presumed to correlate with the cell adhesion and mobility.