The existence of two acute myeloid leukaemia classification systems-one put forth by WHO and one by the International Consensus Classification in 2022-is concerning. Although both systems appropriately move towards genomic disease definitions and reduced emphasis on blast enumeration, there are consequential disagreements between the two systems on what constitutes a diagnosis of acute myeloid leukaemia. This fundamental problem threatens the ability of heath-care providers to diagnose acute myeloid leukaemia, communicate with patients and other health-care providers, and deliver appropriate and consistent management strategies for patients with the condition. Clinical trial eligibility, standardised response assessments, and eventual drug development and regulatory pathways might also be negatively affected by the discrepancies. In this Viewpoint, we review the merits and limitations of both classification systems and illustrate how the coexistence, as well as application of both systems is an undue challenge to patients, clinicians, hematopathologists, sponsors of research, and regulators. Lastly, we emphasise the urgency and propose a roadmap, by which the two divergent classification systems can be harmonised., Competing Interests: Declaration of interests RMS has served in a consulting or advisory role for Bristol Myers Squibb, Curio Science, Gilead Sciences, and Sciences, Servier, and Rigel. ND has received research funding from Daiichi Sankyo, Bristol Myers Squibb, Pfizer, Gilead, Sevier, Genentech, Astellas, Daiichi Sankyo, AbbVie, Hanmi, Trovagene, Fate Therapeutics, Amgen, Novimmune, Glycomimetics, Trillium, and ImmunoGen. ND has served in a consulting or advisory role for Daiichi-Sankyo, Bristol Myers Squibb, Arog, Pfizer, Novartis, Jazz Pharmaceuticals, Celgene, AbbVie, Astellas, Genentech, Immunogen, Servier, Syndax, Trillium, Gilead, Amgen, Shattuck labs, and Agios. JKA has received institutional research funding from AbbVie, Agios, ALX Oncology, Amgen, Amphivena, Aprea AB, Aptose Biosciences, Astellas Pharma, BioSight, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Cyclacel, Fujifilm, Immunogen, Kartos Therapeutics, Kura Oncology, Loxo, Pfizer, and Telios; has served in a consulting or advisory role for AbbVie, Astellas Pharma, BioSight, Bluebird Bio, Curio, Gilead, Kura Oncology, Kymera, Stemline Therapeutics, and Syros; and has served on a data monitoring committee for GlycoMimetics. DAP has served as a consultant or advisor for AbbVie, Novartis, Karyopharm, Syndax, Jazz, Syros, Bristol Myers Squibb, BeiGene, Bergen Bio, Arcellx, Genentech, Immunogen, AstraZeneca, Kura, Ryvu, Magenta, Qihan, Zentalis, Medivir, Hibercell, Link, Daiichi Sankyo, Schrodinger, Aptevo, Rigel, Sumitomo, Adicet, Gilead, and Oncoverity; he has received research funding from AbbVie, Karyopharm, Teva, and Bristol Myers Squibb. TB has served as a consultant or advisor for Pfizer and Takeda. VRB reports participating in safety monitoring committee for protagonist. VRB receives consulting fees from Imugene, research funding from AbbVie, Pfizer, Incyte, Jazz Pharmaceuticals, and National Marrow Donor Program, and provided drug from Chimerix for a trial. AdlFB received research funding from Janssen-Cilag, Novartis, BTG Pharmaceuticals, and AbbVie; has served on advisory boards for Abbvie, Astellas, Bristol Meyers Squibb, Curis, Daiichi Sankyo, Incyte, Immunogen, Jazz Pharmaceuticals, Novartis, Pfizer, Roche, and Servier. AdlFB has received speakers' fees from Abbvie, Astellas, Celgene-BMS, Daiichi Sankyo, Incyte, Janssen Cilag, Jazz Pharmaceuticals, Novartis, Pfizer, Roche, and Servier. HEC received research funding from Celgene and has served as a consultant or advisor for Bristol Myers Squibb, Jazz Pharmaceuticals, Novartis, Daiichi, Genentech and Stemline. She has received speakers fees from Jazz, Novartis, BMS and Stemline; she has been on Data Safety Monitoring Board Committees for AbbVie, ASTEX, Syndax, and Takeda. FEC has received institutional research funding from Celgene, Bristol Myers Squib, Amgen, Fibrogen, Sumitomo Pharma Oncology, and AbbVie, and is a consultant for the Association of Community Cancer Centers. ATF has received research funding from Celgene, AbbVie, and Servier, and has served in a consulting or advisory role for Genentech, Celgene, Foghorn, Kite, Morphosys, AbbVie, Takeda, Ipsen, Forma, Amgen, Novartis, Astellas, Immunogen, Mablytics, EnClear, Orum, PureTech, Pfizer, Daiichi Sankyo, Minovia, Rigel, and Servier. IG has received research funding from Merck, Amgen, Gilead, Incyte, and Genentech, and has served as a consultant and advisor for Immunogen, Bristol Meyer Squibb, Amgen, ClearView, Curio, and Nkarta. MRG has stock ownership in Medtronic, received research support from Incyte and Jannsen, and received consulting fees from AbbVie, Amgen, Astellas, Blueprint Medicines, Bristol Myers Squibb, Cardinal Health, CTI BioPharma, Daiichi Sankyo, Gamida Cell, Genentech, Gilead, GSK, Sierra Oncology, Incyte, Invitae, Jazz, Karius, Novartis, Ono Pharmaceutical, Pfizer, Pharmacosmos, Premier, Servier, and Stemline Therapeutics. BAJ has served as a consultant and advisor for AbbVie, Bristol Meyers Squibb, Daiichi Sankyo, Genentech, Gilead, GlycoMimetics, Jazz, Kymera, Pfizer, Rigel, Servier, and Takeda; was on the protocol steering committee for GlycoMimetics, data monitoring committee for Gilead; and received travel reimbursement and [ support from AbbVie and Rigel; BAJ received institutional research funding from AbbVie, Amgen, Aptose, AROG, Bristol Meyers Squibb, Celgene, Daiichi Sankyo, F Hoffmann-La Roche, Forma, Forty Seven, Genentech, Gilead, GlycoMimetics, Hanmi, Immune-Onc, Incyte, Jazz, Loxo Oncology, Pfizer, Pharmacyclics, Sigma Tau, and Treadwell. GNM has received research funding from Bristol Meyers Squibb, Celgene, Glycomimetics, Forty Seven, Jazz, Astex, Syndax, Immune Onc, and Immunogen; has served as a consultant and advisor for AbbVie, Agios, Macrogenics and Pfizer, and has served on a scientific advisory committee for Abbvie, Agios, Astellas, Bristol Myers Squibb, Forty Seven, Genentech, and Stemline. JM has received institutional research funding from Incyte, Novartis, Bristol Meyers Squibb, CTI Bio, Geron, AbbVie, Kartos, and PharmaEssentia, and has received consulting fees from Bristol Meyers Squibb Incyte, Novartis, Roche, CTI Bio, Geron, Kartos, GSK, MorphoSys, PharmaEssentia, Imago, and Galecto. LCM has received institutional research funding from Jazz Pharmaceuticals, has served in a consulting or advisory role for AbbVie, Curio Science, Celgene Corp, Sierra Oncology, and Nkarta; has received honoraria from the American Society of Hematology, the American Board of Internal Medicine, and the Society of Hematologic Oncology; received royalties from Wintrobe's Publishing; and has served as an expert witness for Incyte Corporation. ASM has served in a consulting or advisory role for AbbVie, Servier, Syndax Pharmaceuticals, Bristol Meyers Squibb, Astellas, Rigel, Zentalis, and Ryvu Therapeutics; has served on a data monitoring safety committee for Jazz Pharmaceuticals, Daiichi Sankyo, and Foghorn Therapeutics; and has served as a medical monitor for the Leukemia and Lymphoma Society Beat AML Study. OP has served in a consulting or advisory role for Scopio Labs, Sysmex America, and F Hoffman-La Roche. KWP Research funding from AbbVie, Agios, Daiichi Sankyo, Millennium; was an advisory board member for AbbVie, Astellas, AstraZeneca, Boston BioMedical, Bristol Myers Squibb, Celgene, Novartis, Roche, Jazz Pharmaceuticals, and Servier. MAS has served on advisory boards for Bristol Meyers Squibb, Novartis, Kurome, and Gilead. CCS has received research funding from AbbVie, Bristol Myers Squibb, Erasca, Revolution Medicines, and Zentalis, and has served on a board of advisory committee for Astellas Pharma, Daichi Sanyko, and Genentech. MSt served on the advisory board for Novartis, Kymera, Sierra Oncology, GSK, and Rigel; consulted for Boston Consulting and Dedham group and participated in GME activity for Novartis, Curis Oncology, Haymarket Media and Clinical care options. MSu receives industry research support from Amgen, Bristol Myers Squibb, Gilead, Janssen, Miltenyi Biotec, Morphosys, Novartis, Roche, Seattle Genetics, and Takeda; serves as a consultant and advisor to AvenCell, CDR-Life, Ichnos Sciences, Incyte Biosciences, Janssen, Molecular Partners, and Takeda; and serves on the speakers' bureau at Amgen, AstraZeneca, Bristol Meyers Squibb, Gilead, GSK, Janssen, Novartis, Pfizer, Roche, and Takeda. GLU served in a consulting role for Novartis and Jazz. MTV received compensation for being a speakers from AbbVie, Bristol Myers Squibb, Astellas, Jazz, Novartis, and Servier; has served in a consulting or advisory role for Jazz and Syros Pharmaceuticals. RBW received laboratory research grants and clinical trial support from Amgen, Aptevo, Celgene, ImmunoGen, Janssen, Jazz Pharmaceuticals, Kura, MacroGenics, and Pfizer; has ownership interests in Amphivena; and served in a consulting role to AbbVie, Adicet, Amphivena, BerGenBio, Bristol Myers Squibb, GlaxoSmithKline, ImmunoGen, Kura, and Orum. ESW has served in a consulting and advisory role for AbbVie, Astellas, Bristol Meyers Squibb, Daiichi Sankyo, Genentech, Gilead, GlaxoSmithKline, Janssen, Jazz, Kite, Kura, Novartis, NuProbe, Pfizer, Rigel, Sellas, and Sumitomo Pharma; has received speaking fees from AbbVie, Astellas, Dava Oncology, Kura Oncology, Novartis, and Pfizer; has served on a data monitoring committee for Abbvie and Gilead; and has served on a research committee for Gilead. JFZ has received honoraria from AbbVie, Bristol Myers Squibb, Daiichi Sankyo, Genentech, Gilead, Immunogen, Servier, and Shattuck Labs; has served as a consultant for AbbVie, Foghorn, Gilead and Servier; and has received research funding from AbbVie, Arog, Astex, Gilead, Jazz, Merck, Shattuck Labs, Stemline, Sumitomo Dainippon Pharma, and Takeda. AZ has served in a consulting or advisory role for AbbVie, Astellas, Jannsen, Novartis, and Pfizer, and received honoraria from AbbVie, Astellas, Jannsen, Novartis, and Takeda. AMZ has served in a consulting or advisory role for AbbVie, Acceleron, Agios, Amgen, Aprea, Astellas, AstraZeneca, BeyondSpring, Boehringer Ingelheim, Cardiff Oncology, Bristol Meyers Squibb, Daiichi Sankyo, Epizyme, Genentech, Gilead, Kura, Incyte, Ionis, Loxo Oncology, Janssen, Novartis; served on clinical trial committees for AbbVie, BioCryst, Bristol Meyers Squibb, Geron, Gilead, Kura, Loxo Oncology, Novartis; has received research funding from AbbVie, Acceleron, ADC Therapeutics, Amgen, Aprea, Astex, Boehringer Ingelheim, Cardiff Oncology, Bristol Meyers Squibb, Incyte, Jasper, Jazz, Novartis, and Pfizer. JPB, RSK, SdB, PD, RD, ND, SDF, MK, TLL, PM, and ACS declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)