Objective: To analyze the cases of acute mastoiditis, characteristics, management and complications in children attended in the emergency department. Methods: Retrospective study of acute mastoiditis in a Spanish tertiary hospital over a 6 -year period (2018-2023). Results: One hundred two episodes of acute mastoiditis were analyzed (54% males, median age 1.8 years). Microorganisms were isolated in one third of cases, mainly Streptococcus pyogenes (64% of ear secretion cultures). Complications occurred in 27.5%, primarily subperiosteal abscess. A younger age, absence of vaccination schedule, previous history of otitis, cochlear implant carriers or white blood cell counts and C -reactive protein levels were not associated with complications. Complicated cases had longer hospitalizations. Treatment included antibiotics, corticosteroids, and surgery in 50% of cases. Conclusions: This study shows an increase of acute mastoiditis during 2023, with a relevant role of S. pyogenes . A younger age, absence of vaccination, personal history of otitis or cochlear implant, blood cell counts and C -reactive protein levels were not associated with complications. (c) 2024 Sociedad Espa & nacute;ola de Enfermedades Infecciosas y Microbiolog & imath;<acute accent>a Cl & imath;<acute accent>nica. Published by Elsevier Espa & nacute;a, S.L.U. All rights reserved.