During the haematogenous spread of tumours, the metastasizing cells must arrest within the blood vessels of the organs they colonize. There is still much debate upon the mechanism of such arrest, whether it is due to mechanical trapping or, more specifically, to adhesion of the tumour cells to the blood vessel wall. This work demonstrates that tumour cells are capable of adhering to blood vessel wall components. According to the hypothesis of specific adhesion, it is thought that metastasizing tumour cells would only come into contact with the vessel wall for a very short time and therefore their adhesion to the vessel wall must be extremely rapid. It has been shown in the past that tumour cells can adhere rapidly to components of the blood vessel wall such as exposed sub-endothelial matrix. Adhesion to endothelial cells was believed to occur at a much slower rate and therefore the involvement of the endothelium during the arrest phase of the metastatic process was thought to be marginal. The experiments carried out during this study show that, in vitro, tumour cells do adhere to the endothelium at a rate comparable to that for isolated components of the sub-endothelial matrix. Furthermore, this work provides some evidence that the molecular basis for such rapid adhesion to the endothelium may be different from the ones involved in the adhesion to known components of the sub-endothelial matrix.