Background: There are no large-scale epidemiological studies on primary hyperparathyroidism (PHPT) in Russia. The high prevalence of the disease, the high risk of disability and death in this cohort of patients requires the study of the epidemiological and clinical structure of PHPT to determine the extent of medical care. AIM: Evaluate the frequency of PHPT detection and characterize its clinical forms in Russia using an online registry. METHODS: The object of the study is the database of the State Register of Patients with PHPT – 1914 patients from 71 regions of the Russian Federation. New cases of the disease, as well as dynamic indicators are recorded when patients visit outpatient clinics or medical institutions. The analysis of data made at the end of December 2017 was carried out. The following parameters were evaluated: demographic and clinical indicators; indicators of phosphorus-calcium metabolism, the main forms of PHPT and its course, the primary characteristic of PHPT in hereditary syndromes and parathyroid carcinoma. Results are presented as mean and standard deviations, or medians and quartiles; descriptive statistics of qualitative attributes – absolute and relative frequencies. RESULTS: the total number of patients with PHPT in the registry on 31 of December 2017 was 1914 cases (0.001% of the population of the Russian Federation). Identification of PHPT was 1.3 cases per 100 thousand of the population in Russia, 7.6 cases in Moscow, 6.1 cases per 100 thousand in the Moscow region. The average age of patients at the time of diagnosis was 55.6 ± 10 years. The active phase of the disease was registered in 84.6% of patients (1620/1914), most of whom had a symptomatic PHPT – 67.1% (1087/1620), and 32.9% – a asymptomatic disease (533/1620). Symptomatic disease with visceral complications was detected in 15.8% cases (172/1087), with bone complications in 48.4% (526/1087). The mixed form of the disease was detected in 35.8% of patients with manifest form (389/1087). Normocalcemic variant PHPT (nPHPT) was registered in 14.5% cases (234/1620). Sporadic PHPT occurs in 83% of cases (1592/1914). 326 patients (17%) had a suspicion for hereditary form of the disease: average age was 31.2 ± 12.3 years. A genetic analysis was conducted in 61 patients (3.2%): showed the mutation in the MEN1 gene in 2.9% of cases (55/1914) and the mutation in the CDC73 gene – in 0.3% of cases (6/1914) (HPT-JT syndrome). Parathyroid carcinoma was confirmed in 1.8% of all patients (35/1914). Surgical treatment was performed in 64.5% of patients (1234/1914). Remission was achieved in 94% of cases (1160/1234), in 6% of cases relapse after surgical treatment or persistence of PHPT was recorded. CONCLUSION: detection of PHPT in the Russian Federation raised in comparison to 2016, which is associated with an active start of registration of patients in the regions. At this stage, it is necessary to modify the principles of registration and control, to make a platform for gathering information and calculating the necessary volumes of medical care for PHPT patients.