Background: To date studies have not been conducted to assess the epidemiological characteristics of Ph-negative myeloproliferative neoplasms, in particular primary myelofibrosis (PMF) in the Russia. Aims: Creation of the Russian registry of primary myelofibrosis to assess the epidemiological clinical molecular characteristics of the PMF. Methods: In 2017 initiated a multicenter prospective observational cohort study involving 14 research centers from 11 regions of Russia. The study included 188 patients: 177 (94%) with PMF, 10 patients with post-PV MF and 1 patient with post-ET MF. Men: women ratio – 1: 1,3. Results: The incidence of PMF in various regions of the Russia ranges from 0.05 to 2.12 per 100000 (Table 1, 2). Among patients with PMF, post-PV MF and post-ET MF, 44% (83) are patients in the age group 60-74 years, 28% (53) in the age group 45-59 years, 17% (32) - patients aged 18-44 years, 11% (20) - in the age group 75-90 years. Constitutional symptoms were recorded in the majority of patients: fatigue - 78% (147), lethargy - 65 (122), headache - 40% (75), discomfort in the stomach - 38% (72), discomfort in the left hypochondrium - 38% (71), night sweats - 32% (61), feeling of early satiety - 30% (56), weight loss - 26% (48), bone pain - 23% (43), sweating - 15% (28), skin itching - 11% (20), fever - 6% (12). No symptoms mediated by the disease - 5% (10). Splenomegaly at the time of diagnosis was recorded in 76% (143 patients). Molecular analysis performed at 94% of patients (176): JAKV617F mutation detected in 122 patients, JAK2exon12 - 1, CALR - 34, MPL - 7, triple negative variant - 13. Allelic burden of JAK2V617F defined in 90 patients with PMF, median - 34% (1 - 100%). Data on allelic burden JAK2V617F was in 7 patients with post-PV MF, the median was 57% (3 - 88%). Histological examination of bone marrow performed by 91% (171 patients). Histochemical studies with an assessment of the degree of reticulin fibrosis - 81% (153). Confirmation of the diagnosis according to the full set of criteria in patients with PMF registered in 54% of patients. The distribution of patients by risk groups in accordance with the IPSS prognostic scale: low - 26%, intermediate-1 - 33%, intermediate-1 - 23%, high - 18%. The first line of therapy: hydroxyurea - 58%, ruxolitinib - 14%, interferon-alpha - 10%, glucocorticosteroids - 5%, erythropoietin 3%, anagrelide - 1%, other therapy - 9%. Blood transfusions performed in 70% of patients, thromboconcentrate transfusions - 6%. Concomitant therapy is given to 63% (119 patients): acetylsalicylic acid - 78, allopurinol - 49, erythropoietin - 11, clopidogrel - 6, NSAID - 3, sulodexide - 3, tranexamic acid - 1, etamzilat - 1, other (dipyridamole, iron preparations, folic acid, vitamin B12) - 30. The efficacy of therapy assessed for 52 patients: complete clinical and hematological remission - 23% (12), partial clinical and hematological remission - 48% (25), stabilization of the disease - 29% (15). 5 deaths reported. The 2-year overall survival rate was 97% (Figure 1). Summary/Conclusion: In general the registry of patients with PMF allows integrating information into a common system and obtaining information characterizing the population of patients with this disease in Russia.