Tumor cell motility is required for invasion and metastasis. The locomotory machinery of the cell includes cell projections called pseudopodia which are regulated by a complicated linkage between cell surface receptors or sensors and the internal cytoskeleton. Recently a new class of motility stimulating cytokines have been identified. These cytokines can function as autocrine motility factors and require a pertussis toxin sensitive G protein pathway to transduce a random motile response.