Idiopathic hypertensia accounts for 90 percent of all chronic hypertension cases. Today, 18-20 percent of the adult population in economically developed countries suffer from hypertension, i.e. their arterial pressure repeatedly increases to 160/95 mm Hg and higher. What causes hypertension is yet to be discovered, though its pathogenesis is partly known. Two factors are believed to be involved in the development of hypertension: noradrenaline and sodium. G.F.Langa's theory on the decisive role of psychic overstrain and psychic trauma in the development of hypertension says that noradrenaline, for instance, plays the role of an effector agent. Hypertension will develop providing there is hereditary predisposition accompanied by some adverse external factors. Epidemiological researches confirm that the degree of obesity and high arterial pressure are linked. The disease seldom affects people younger than 30 and older than 60. If a young man has steady systolodiastolic arterial pressure there are good reasons to expect secondary, notably renovascular, hypertension. As to people older than 60-65, high systolic pressure (160-170 mm Hg) given normal or reduced diastolic pressure usually deals with aorta atherosclerotic inspissation. Hypertension progresses chronically and has periods of aggravation and remission. The disease may progress at a different pace. The disease can be slowly-progressing (benign) and rapidly-progressing (malignant). In accordance with the hypertension classification used by the World Health Organisation (WHO), the slowly-progressing form experiences three stages. Stage 1 (mild) is characterised by a relatively slight rise in arterial pressure, within 160-179 (180) mm Hg (systolic), 95-104 (105) mm Hg (diastolic). The arterial pressure level is unstable, when resting it normalises gradually. Some patients feel normal, others have headaches, head noises, insomnia, reduced mental efficiency, etc. Patients may occasionally feel random dizziness and have nasal haemorrhages. The symptoms of the left ventricle's hypertrophy are usually not observed. Stage 2 (moderate) features higher and more stable arterial pressure, which, when at rest, is within 180-200 mm Hg (systolic) and 105-114 mm Hg (diastolic). Patients often complain of headaches, dizziness and pain in the region of the heart, often stenocardic in character. Hypertensive crises are typical of this stage. Symptoms of the affection of the so-called target-organs become noticeable: hypertrophy of the left ventricle (sometimes only interventricular septa), weakening of the 1st tone at the apex of the heart and accented 2nd tone in the aorta. Some ECGs show subendocardial ischemia. The central nervous system displays vascular insufficiency and transitional brain ischemia. Brain insults are possible. As to the eyeground, the arterioles narrow, the veins compress and expand. Haemorrhages and exudates can be observed. The renal bloodstream and the speed of glomerular filtration are reduced, though uroscopy shows no departure from the norm. Stage 3 (severe) is characterised by frequent vascular disorders caused by high and stable arterial pressure and progressing arteriolosclerosis and atherosclerosis of larger vessels. Arterial pressure amounts to 300 mm Hg (systolic), 115-129 mm Hg (diastolic). Arterial pressure never normalises spontaneously. The clinical picture shows the affection of the heart (stenocardia, myocardial infarction, insufficient blood circulation and arrhythmia), brain (ischemic and hemorrhagic infarcts, encephalopathy), eyeground (angioretinopathy, type 2 and 3), kidneys (reduced renal bloodstream and glomerular filtration), etc. Some patients suffering from 3rd stage hypertension do not have severe vascular complications for years, despite high and stable arterial pressure.