The Rho-kinase inhibitor, Y-27632, inhibited in vitro chemotactic migration to bone marrow fibroblast conditioned media and metastatic growth in immune-compromised mice of highly invasive human prostatic cancer (PC3) cells. Y-27632 also reduced myosin light chain phosphorylation and markedly altered the morphology of cells that developed numerous processes containing microtubules. A strikingly different, rounded phenotype was induced by an inhibitor of myosin light chain kinase, ML9. The M_110–130 subunit of the myosin phosphatase that is regulated by Rho-kinase was present in PC3 cells that contained significantly more RhoA than the less invasive, LNCaP cells. Y-27632 also inhibited angiogenesis as measured by endothelial cell tube formation on Matrigel. We conclude that invasiveness of human prostate cancer is facilitated by the Rho/Rho-kinase pathway, and exploration of selective Rho-kinase inhibitors for limiting invasive progress of prostate cancer is warranted.