The International Network for Pediatric Hemophilia (INPH) comprises a group of physicians committed to the unique care of and challenges facing pediatric hemophilia patients. By collaborating on an international level, extensive experience can be shared on current practice, new trends can be discussed and scientifically valid studies can be developed and performed. The three overall objectives of the group (scientific progress, education and networking) are achieved at each annual meeting starting with a round table on the members’ current research and clinical activities, project reports of INPH study initiatives, followed by invited educational presentations and interactive discussions. The meetings close with proposals of new projects, future directions of the group and concluding remarks. The Fourth Annual INPH meeting, held in 2009 in Boston, MA, USA, focused on inhibitor development and hemophilic arthropathy in the clinical care of children with hemophilia.