To investigate whether there are differences in haematology and coagulation indices in arterial and venous plasma, and whether those changes related to damage to the endothelium in atherosclerosis, we obtained blood samples from 22 subjects undergoing diagnostic angiography. There were no differences in any of the 15 routine haematological indices measured. There were no differences in prothrombin time, activated partial thromboplastin time, fibrinogen, tissue plasminogen activator, D-dimer, leucocyte elastase, soluble P-selectin or von Willebrand factor. In venous samples, von Willebrand factor was lower in serum than in plasma (p < 0.0001). Levels of the tissue plasminogen activator/plasminogen activator inhibitor-1 (tPA/PAI-1) complex were markedly higher in arterial blood than in venous blood (p = 0.004) and plasma viscosity was higher in venous blood (p = 0.0014). Consequently, with the exception of viscosity and the tPA/PAI complex, we can find no differences in arterial blood compared to venous blood which can contribute to the debate regarding the mechanism of damage to arterial endothelial cells but the relative protection of venous endothelial cells from injury in atherosclerosis.