Four human colon adenocarcinoma cell line variants with different metastatic potential were used to examine whether a correlation exists between actin level, state of actin polymerization and invasiveness of tumour cells. Monomeric (G), total (T) and filamentous (F) actin were determined in the cytosolic fraction of these cells. A statistically significant decrease in G actin level and increase in the state of actin polymerization (measured by F:G actin ratio) were found in the cytosol of three cell variants with higher metastatic potential and invasiveness (EB3, 3LNLN, 5W) compared with the parental cell line (LS180). Our experimental data lead to the conclusion that there is a correlation between the metastatic capacity of human colon adenocarcinoma cells and the state of actin polymerization.