The essential problem of the vicious circle leading to end-stage cardiovascular disease is atherosclerosis. This paper focuses on the functional changes centred on the endothelium that accompany the development of atherosclerosis, examining in particular pathological alterations in the L-arginine/nitric oxide (NO) pathway. Changes in the NO system are associated with altered platelet and monocyte interactions with the vessel wall, abnormal vasoconstriction and altered vascular structure. Diabetes, hyperglycaemia, hypertension and hypercholesterolaemia are all involved in this process. Endothelin is a vasoconstrictor peptide produced by endothelial cells which is upregulated under these conditions. Normalising endothelial function could involve platelet inhibition, lipid-lowering agents to prevent foam cell formation and decrease the lipid load of the blood vessel wall, and agents to interfere with some of the mechanisms involved in vasoconstriction, proliferation and migration, including ACE-inhibitors and angiotensin receptor antagonists, and possibly new tools such as endothelin receptor antagonists.