Metastasis of tumours is a sequence of events taking place after the appearance of a primary tumour. The potency of a tumour to metastasise greatly depends on the molecular interactions between tumour components (cellular differentiation and heterogeneity, surface antigenic determinants etc.) and the micro-environment. The complexity and diversity in the composition of tissue micro-environment is in great extent determining the metastatic behaviour or a primary tumour. Extracellular matrix composition, rearrangement of cytoskeleton, cell antigenicity , expression of metastasis-related novel genes, cell adhesion and novel therapeutical approaches such as blockage of angiogenesis, are the major topics discussed in detail in this volume.