BackgroundRecent studies show contradictory data on the incidence of hospitalizations for acute bronchiolitis (AB) and an escalating increase in public health burden. Aims and objectivesWe aimed to analyze the population-based admission rate for AB in children under 2 years of age, in Portuguese public hospitals, from 2000 to 2015, to assess trends and regional variations in admission rate; outcomes; associated direct health-care costs; and changes in management after the implementation of national guidelines. MethodsRetrospective observational study, conducted using a Portuguese administrative database, which contains all registered public hospitalizations in mainland Portugal, and demographic data from the National Statistics Institute. ResultsOver the study period, we recorded 80,491 admissions for AB. The mean admission rate was 26.28 and was higher in the northernmost regions of the country. Along the time, the admission rate rose by an average of 1.6% per year (3.8% in children younger than 3 months) and the average length of stay (LOS) was 6.1 days and decreased, to a minimum of 5.5 days in 2014. The in-hospital mortality rate (0.1%) and the use of invasive ventilation remained stable, but non-invasive ventilation use increased from 0.4% in 2000 to 4% in 2015. The direct estimated total costs were of 72,420,732€. In recent years, there was a decrease in the reported tests and procedures. ConclusionsAB remains a major burden in the healthcare system. The admission rate increased but does not seem to be due to an increase in severity, as LOS decreased, and the use of invasive ventilation and mortality remained unchanged.