The spectrum of disorders associated with arterial hypertension (AH) encompasses chronic uncomplicated hypertension and the hypertensive crises, including hypertensive urgences and emergencies. Hypertensive crises accounted for more than 25% of all patient visits to a medical section of an emergency department, with hypertensive urgences (HU) accounting for two-third of these cases. Hypertensive crises, without prompt treatment, are often associated with morbidity and mortality. We propose to conduct a population-based case-control study of HU in areas of the Russian Federation. We will include about thirty study centers and one data coordinating center and will recruit study participants over a period of one years. We plan to conduct in-person interviews with 1,500 cases and 1,500 controls to elicit information on demographic background and history of exposures. We intend to test about 20-25 risk factors of HU thus calculated target number of subject is 3000 pts. We`re going to get access to hospital lists in each study center. From the database we`ll select patients with AH and recruit every third participant who came to hospital or/and policlinic. Every selected participant will be asked to respond to some questions by phone and be divided into two groups. Participants who have HU two weeks before the call will be questioned about level of arterial pressure and treatment during HU. Participants with often HU (every week or more) will be included into first group (prevalent cases, group A). Participants with seldom HU (every month or less) will be included into second group (controls, group B). Cases and controls will be selected from the same population of AH patients. Questionnaire contains information about age, gender, tobacco use, data about HU (frequency, treatment and its complications), antihypertensive and concomitant treatment, level of blood pressure, regularity of taking antihypertensive drugs, associated clinical conditions (cerebrovascular disease, heart disease, renal disease, peripheral vascular disease), PCI, CABG, if it be possible we intend to collect information of factors influencing prognosis (fasting plasma glucose, dyslipidaemia, serum creatinine, serum uric acid, left ventricular hypertrophy).