The realization that there is a very close relationship between tumours and blood vessels goes back to the very first description of this group of diseases. The term angiogenesis was first used in 1787 to describe new blood vessels emerging from an existing vasculature and in 1971 the hypothesis that tumour growth is always dependent on angiogenesis was proposed. Eventually in 2000, ‘sustained angiogenesis’ was included as one of the six original hallmarks of cancer but, this turned out not to be true as in 1996 clinically detectable, grown up non-angiogenic primary and metastatic tumours were formally described by our laboratory. The ability of these tumours to exploit and co-opt pre-existing vessels has been confirmed in a variety of organs and a new field in cancer biology has opened. This seminar will summarise what we know about the biology of these tumours and of the vessel co-option process.