Acquired Aplastic Anaemia (AA) is a rare heterogeneous disease characterized by pancytopoenia and hypoplastic bone marrow. The incidence is 2-3 millions per year (all age groups) in Europe, but is higher in East Asia. The pathogenesis of AA is complex and involves haematopoietic stem cell/progenitor cell deficiencies and autoimmune mechanism. Survival in severe aplastic anaemia (SAA) has markedly improved in the past 2 decades because of advances in haematopoietic stem cell transplantation, immunosuppressive and biologic drugs, and supportive care. In SAA haematopoietic stem cell transplant (HSCT) from a matched sibling donor (MSD) is the treatment of choice. If a MSD is not available, the options include immunosuppressive therapy (IST) or unrelated donor HSCT. The objective of this guideline is to provide healthcare professionals with clear guidance on the diagnosis and management of paediatric patients with AA. A preliminary, evidence-based document issued by a group of paediatric haematologists was discussed, modified and approved during a series of "Consensus Conferences" according to procedures previously validated by the AIEOP Board. The guidelines highlight the importance of referring paediatric patients with AA to paediatric centres with long experience in diagnosis, differential diagnosis, management, supportive care and follow-up of AA; haematopoietic stem cell transplantation as first line therapy if an MSD is identified; the use of first-line IST containing horse anti-thymocyte globulin and cyclosporine A (CsA) if an MSD is not identified.