Primary myelofibrosis is a rare myeloproliferative neoplasm that affects 0.2-1.5 people per 100,000. As a rule, the diagnosis is confirmed after 60 years, but recently, hematologists around the world have encountered the problem of primary myelofibrosis in young people. The classic manifestations of myelofibrosis are characterized by splenomegaly, cytopenia, and bone marrow fibrosis, but in patients younger than 40 years, the diagnosis is most often made in the prefibrotic stage of the neoplasm. The aim of the paper is to identify and evaluate the clinical and hematological features of primary myelofibrosis in young patients in the prefibrotic stage.