PE can occur following HCT. However, the incidence, etiology, risk factors, and treatment remain unclear. We performed a retrospective study evaluating 355 pediatric recipients of HCT treated at a single institution between January 2005 and August 2010. No cases of PE were identified in the autologous HCT (auto-HCT) recipients (0/43), while 19% (57/296) of allogeneic HCT (allo-HCT) developed PE. Among the 57 PE patients, 40 (70%) were males; the median age at transplantation was 6.6yr (0.117.3yr). Thirty-six patients (63%) had significant PE with 23 patients (40%) treated by pericardiocentesis, and 19 (33%) experiencing recurrent PE. OS rates for patients who developed PE were 84% at 100days and 65% at threeyr after HCT. Risk factors associated with PE on multivariate analysis included myeloablative conditioning (p=0.01), delayed neutrophil engraftment (p<0.01), and CMV+serostatus of the recipient (p=0.03). Recipients with non-malignant diseases were significantly less likely to die after development of PE (p=0.02 and 0.004 when comparing with standard and high-risk diseases, respectively). In summary, PE is a common and significant complication of pediatric allo-HCT. Prospective studies are needed to better determine the etiology and optimal method of PE treatment after HCT.