Polycythaemia vera is associated with a reduced quality of life, a high rate of vascular events, and an intrinsic risk of disease evolution. The results of several randomised trials for the treatment of this disorder are now available, and both a new ropegylated formulation of interferon alfa-2b (ropeginterferon alfa-2b; 2018) and ruxolitinib (2015) have been approved in Europe. European LeukemiaNet (ELN) investigators have therefore deemed it appropriate to provide recommendations for the use of these drugs in clinical practice. An expert panel of 14 senior haematologists from ELN centres that had actively participated in previous ELN projects or relevant randomised trials, chaired by a member of the ELN Steering Committee, developed a list of clinical questions, and a methodologist established three patient, intervention, comparator, outcome (PICO) questions and systematically reviewed the evidence. Recommendations were approved by six Delphi consensus rounds and two virtual meetings (on Jan 26, 2021, and June 24, 2021). The expert panel recommended that patients with polycythaemia vera who are younger than 60 years and have not had previous thrombotic events should start cytoreductive drug therapy if at least one of the following criteria are fulfilled: strictly defined intolerance to phlebotomy, symptomatic progressive splenomegaly, persistent leukocytosis (>15 × 10 9 white blood cells per L), progressive leukocytosis (at least 100% increase if baseline count is <10 × 10 9 cells per L or at least 50% increase if baseline count is >10 × 10 9 cells per L), extreme thrombocytosis (>1500 × 10 9 platelets per L), inadequate haematocrit control requiring phlebotomies, persistently high cardiovascular risk, and persistently high symptom burden. Recombinant interferon alfa, either in the form of ropeginterferon alfa-2b or pegylated interferon alfa-2a, is the recommended cytoreductive treatment for these patients. The expert panel suggested that either interferon alfa or ruxolitinib should be considered for patients who are being treated with hydroxyurea but require a therapy change., Competing Interests: Declaration of interests MM has received consulting fees from Gilead Sciences, speaker fees from Amgen, support for attending meetings from Takeda, and is a member of the guideline committee of the Italian Society of Hematology. AMV has received speaker fees from Novartis, AOP Health, Incyte, AbbVie, GlaxoSmithKline (GSK), and Bristol Myers Squibb (BMS); and has participated on the advisory boards of Novartis, Incyte, AOP Orphan Pharmaceuticals, AbbVie, GSK, BMS, and Roche. MG has received consulting and speaker fees, support for attending meetings, and participated on advisory boards for AOP Health, Novartis, Celgene, Amgen, AstraZeneca, CTI BioPharma, Shire, Pfizer, Roche, Janssen Pharmaceuticals, and Gilead Sciences. CH has received grants or contracts with payment to her institution from Novartis, Celgene, and Constellation Pharmaceuticals; consulting fees from Keros Therapeutics, Galecto Biotech, and Roche; speaker fees from Novartis, Celgene, CTI BioPharma, AbbVie, Gilead Sciences, Janssen Pharmaceuticals, Promedior, and Geron Corporation; support for attending meetings from Novartis and Celgene, and has participated on advisory boards for Roche, CTI Biopharma, Geron Corporation, Promedior, AbbVie, AOP Orphan Pharmaceuticals, and Galecto. SK has received research grants from AOP Health, Novartis, Janssen Pharmaceuticals, and Imago BioScience; consulting fees from Pfizer, CTI BioPharma, Sanofi, Novartis, BMS/Celgene, Incyte/ARIAD, Roche, AOP Orphan Pharmaceuticals, and Janssen Pharmaceuticals; speaker fees from Pfizer, CTI BioPharma, Sanofi, Novartis, BMS/Celgene, Incyte/ARIAD, Roche, AOP Orphan Pharmaceuticals, Janssen Pharmaceuticals, Kartos Therapeutics, and Imago BioScience; support for attending meetings from Alexion Pharmaceuticals, Novartis, BMS/Celgene, Incyte/ARIAD, AOP Orphan Pharmaceuticals, CTI BioPharma, Pfizer, Sanofi, Janssen Pharmaceuticals, Geron Corporation, Kartos Therapeutics, Sierra Oncology, Imago BioScience; has participated on advisory boards for Pfizer, CTI BioPharma, Sanofi, Novartis, BMS/Celgene, Incyte/ARIAD, Roche, AOP Orphan Pharmaceuticals, Kartos Therapeutics, and Imago BioScience; has patents planned, issued, or pending from Rheinisch-Westfalische Technische Hochschule Aachen; and has a leadership role in Deutsche Gesellschaft fur Hamatologie und Medizinische Onkologie. HG has received research grants and support for attending meetings from AOP Orphan Pharmaceuticals and Novartis; consulting fees from AOP Orphan Pharmaceuticals, Novartis, and BMS/Celgene; and speaker fees from AOP Orphan Pharmaceuticals, Novartis, BMS/Celgene, and Janssen. AÁ-L has participated on advisory boards and has received speaker fees from Novartis, AOP Orphan Pharmaceuticals, and Celgene; and has received support for attending meetings from Novartis and Pfizer. VDS has received speaker fees from AbbVie and Novartis, and participated on advisory boards of AOP Health and Novartis. PG has received speaker fees from AbbVie and Novartis, and support for attending meetings from Sanofi. FPal has received speaker fees from Novartis and Incyte; consulting fees from AOP Health, CTI BioPharma, Novartis, and Celgene/BMS; and support for attending meetings from Celgene/BMS. FPas has received consulting fees from AbbVie, Novartis, BMS, and Amomed Pharma; and speaker fees from AbbVie, Janssen Pharmaceuticals, Novartis, and BMS. RTS has received research grants from the Cancer Research & Treatment Fund and Johns Family Fund, received speaker fees and payment for expert testimony from PharmaEssentia, participated on an advisory board for PharmaEssentia, and has a leadership role (Vice-President and Medical Director) at the Cancer Research & Treatment Fund. J-JK received consulting fees from AbbVie and Novartis; speaker fees from AOP Orphan Pharmaceuticals, Novartis, and BMS; and has participated on advisory boards for Incyte. TB has received research grants and speaker fees from AOP Orphan Pharmaceuticals and Novartis, and consultancy fees from AOP Orphan Pharmaceuticals. GB and RH declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)