Introduction. 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. Material and methods. A retrospective study was performed on clinical cases of primary myelofibrosis, registered at the Oncological Institute of the Republic of Moldova. The diagnosis was confirmed according to 2016 WHO criteria based on histological and molecular studies. We enrolled young patients under the age of 40 who had been diagnosed with prefibrosis in our study and analyzed them for clinical manifestations and complete blood count parameters. To optimize the analysis, all patients were divided into two groups according to their age: 18–29 and 30–40 years old. Results. Changes in the complete blood count, manifested by thrombocytosis and leukocytosis, are the main laboratory patterns of primary myelofibrosis in young patients in the prefibrotic stage. The most relevant clinical features are splenomegaly and hepatomegaly, but no correlation between these manifestations has been found. Conclusions. The classical clinical and hematological characteristics of primary myelofibrosis do not specify lowand intermediate-risk patients’ management in the prefibrotic stage, as compared with the other chronic myeloproliferative BCR-ABL-negative neoplasms. The proliferation type of primary myelofibrosis is characteristic for young patients with pre-fibrotic stage. According to our results, the main manifestations in the prefibrotic stage are detected in a complete blood count and comprise anemia, leucopenia, leukocytosis, and thrombocytosis.