Standard blood pressure should reach the values 120/80 mmHg. But in result of the effect of a lot of factors the blood pressure goes up, and obscure, but serious disease - hypertension (HT) or high blood pressure develops. The pressure exceeding 140 (systolic) and 90 (diastolic) mmHg is indicated as HT.. In diabetics and pregnant women the criterion is stricter - 135/80 mmHg. The patients in whom HT was diagnosed should monitor and check their blood pressure constantly. The tonometers serve for this purpose. They may be mercurial or digital. The mercurial tonometers are more accurate, but they are more demanding for handling. They use Korotek's method of taking blood pressure. The cuff is arm, and the phonendoscope always belongs to accessories. Digital tonometers are less accurate, but their attendance is easier. The pressure is measured oscilometrically, exceptionally in combination with the Korotek method. The cuff can be arm or wrist.