DEVELOP is a multicenter, international, prospective, observational registry of the long-term safety and clinical status of 6070 pediatric patients (pts) with inflammatory bowel disease (IBD) diagnosed prior to 18 years of age who were treated with anti-tumor necrosis factor biologics (aTNF) and/or other medical therapies for IBD. Our aim was to assess the risk factors that lead to first serious infection (SI): an infection requiring hospitalization and/or IV therapy.