Advances in our understanding of the mechanisms of lamellipodia and filopodia assembly have led to a better concept of how cells move, including how the actin cytoskeleton might be important for the motility of metastatic cancer cells. The cytoskeleton is a potentially interesting target for prevention of invasion and metastasis. As key proteins are uncovered which regulate the assembly of actin-based structures, these need to be considered in light of whether they represent potential invasion and metastasis proteins.