Retinal blood vessels differ from most other vessels in the body (with the exception of those in the brain) in two important respects. The first is the presence of blood-retinal barriers, best illustrated by fluorescein angiography. The second important difference is that retinal vessels do not have sympathetic innervation and blood flow is modulated by autoregulation mechanisms. In 1939 Keith, Wagener and Barker proposed a classification system for hypertensive retinopathy which was innovative and of prognostic importance at that time. However, the different features of hypertensive and arteriosclerotic vasculopathies are not adequately distinguished by this classification system. Clinical features of accelerated hypertension are retinal haemorrhages, cotton wool-spots, hard exudates, papilloedema and increased vascular permeability. These must be differentiated from features associated with arteriosclerosis which are arteriovenous crossing changes and arterial constriction. The advantages of the Hogan classification system, based up on histopathologic and pathogenetic considerations are discussed. Other retinal vascular diseases associated with hypertension are also mentioned. Such as toxaemia of pregnancy, arterial macroaneurysm and anterior ischaemic optic neuropathy. Retinal branch vein occlusion is rather associated with arteriosclerosis than with hypertension.