Background and aims: Acute severe ulcerative colitis (ASC) is a potentially life-threatening event. Poor pediatric data are available about the success rates of Infliximab (IFX) as a second line therapy. This study was performed in consecutively observed pediatric patients with ASC, treated according to the 2011 European Crohn's colitis Organization (ECCO)- European Society for Pediatric Gastroenterology, Hepatology and nutrition (ESPGHAN) guidelines on pediatric ASC¹ and aim to assess the long-term efficacy of IFX and clinical predictors of poor outcome.||Methods: Children hospitalized for an episode of ASC, defined as a Pediatric Ulcerative Colitis Activity Index (PUCAI) of at least 65 points, were enrolled. Clinical assessment through PUCAI and laboratory data (Erythrocyte Sedimentation Rate, C-Reactive Protein, hemoglobin, albumin, hematocrit, ferritin) was recorded at admission and at day 3 and 5. All patients were treated according to the above mentioned guidelines for ASC and received intravenous (iv) corticosteroids (CS) as first-line therapy. IFX was administered as second-line therapy in CS-refractory patients. In a 2-year follow up the overall colectomy rate and the efficacy of IFX in avoiding colectomy were evaluated.