Metastasis and tumor angiogenesis are invasive phenomena and share many common properties at the physiological level and some similarities at the molecular level. Each consists of repetitive cycles of interaction with adjacent extracellular matrix components by mediating cellular adhesion, matrix dissolution, and cellular motility to achieve metastasis of cancer cells or neovascularization of tumors. Molecular factors which implement this triad of events are reviewed, as are several signal transduction components which may regulate them. Some potentially promising prognostic, diagnostic, and therapeutic modalities for tumor angiogenesis and metastatic disease are also discussed.