It is well known that blood pressure (BP) exhibits diurnal variation. Nocturnal fall of BP normally exceeds 10%. Subjects with such fall of BP during sleep are classified as "dippers" and those with a nocturnal fall of BP less than 10% are classified as "non-dippers". Non-dippers are exposed to a greater cardiovascular risk. To date dipping status is defined with 24-hour ambulatory BP monitoring (ABPM). Many studies have shown that Home BP monitoring (HBPM) can be an alternative to daytime ambulatory BP monitoring and it exhibits similar correlation to markers of hypertension target-organ-damage (TOD). Nocturnal hypertension shows closer correlation with TOD, than daytime hypertension. In this study patients will be provided with a new-technology, reliable oscillometric device for HBPM, equipped with a modified algorithm, which allows scheduled automated BP measurements during sleep (Microlife WatchBP Home Nocturnal). Duplicate morning and evening BP measurements with one-minute interval will be performed by the patient sitting during seven working days. Afterwards a 24-hour ABPM will be performed, using Microlife WatchBP O3 oscillometric device, with a 20-minute interval between measurements. This order may be reversed according to the wish of the patient and devices' availability. Participants will visit site 3 times. Office blood pressure will be measured during two visits. Triplicate measurements with Microlife WatchBP Home Nocturnal will be performed at the sitting position.