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• Toxicity reduction with outcome preservation is a goal of myeloablative TBI in children. • Fractionated TBI of 12–14.4 Gy, in 1.6–2 Gy fractions b.i.d. is advisable for children. • When possible, dose reduction to lungs (<8 Gy), kidneys (≤10 Gy) and lenses (<12 Gy) is appropriate. • Setup considerations for conventional and highly conformal TBI techniques in children. • Cooperation can support new insights, research and implementation of new techniques. Myeloablative Total Body Irradiation (TBI) is an important modality in conditioning for allogeneic hematopoietic stem cell transplantation (HSCT), especially in children with high-risk acute lymphoblastic leukemia (ALL). TBI practices are heterogeneous and institution-specific. Since TBI is associated with multiple late adverse effects, recommendations may help to standardize practices and improve the outcome versus toxicity ratio for children. The European Society for Paediatric Oncology (SIOPE) Radiotherapy TBI Working Group together with ESTRO experts conducted a literature search and evaluation regarding myeloablative TBI techniques and toxicities in children. Findings were discussed in bimonthly virtual meetings and consensus recommendations were established. Myeloablative TBI in HSCT conditioning is mostly performed for high-risk ALL patients or patients with recurring hematologic malignancies. TBI is discouraged in children <3–4 years old because of increased toxicity risk. Publications regarding TBI are mostly retrospective studies with level III–IV evidence. Preferential TBI dose in children is 12–14.4 Gy in 1.6–2 Gy fractions b.i.d. Dose reduction should be considered for the lungs to <8 Gy, for the kidneys to ≤10 Gy, and for the lenses to <12 Gy, for dose rates ≥6 cGy/min. Highly conformal techniques i.e. TomoTherapy and VMAT TBI or Total Marrow (and/or Lymphoid) Irradiation as implemented in several centers, improve dose homogeneity and organ sparing, and should be evaluated in studies. These ESTRO ACROP SIOPE recommendations provide expert consensus for conventional and highly conformal myeloablative TBI in children, as well as a supporting literature overview of TBI techniques and toxicities. [ABSTRACT FROM AUTHOR]