Infection is the leading cause of morbidity and mortality in the first year following lung transplantation. HG after adult lung transplantation has been associated with increased infections and hospitalization as well as decreased survival. The purpose of this study is to define the incidence, risk factors, and outcomes of HG in the first year following pediatric lung transplantation. A retrospective review of all lung transplant recipients at a single pediatric center over a four-yr period was performed. All serum Ig levels drawn within one yr of transplantation were recorded. An association between HG during the first year after transplantation and age, race, gender, diagnosis leading to transplantation and clinical outcomes including hospitalization, infections requiring hospitalization, viremia, fungal recovery from BAL lavage, and mortality was sought. HG was defined using age-based norms. Fifty-one charts were reviewed. Mean (+/- s.d.) post-transplantation levels for IgG, IgA, and IgM were 439.9 +/- 201.3, 82.3 +/- 50.2, and 75.2 +/- 41.4 mg/dL, respectively. HG was present in 48.8%, 12.2%, and 17.1% of patients for IgG, IgA, and IgM, respectively. Patients with HG for IgG were older (14.3 +/- 3.8 vs. 9.2 +/- 5.4 yr; p < 0.01). IgA and IgM HG were associated with invasive aspergillosis (p < 0.01 and p = 0.05, respectively). IgG and IgM levels inversely correlated with bacterial infections and hospital days, respectively (p < 0.01, p < 0.05). HG is a frequent complication following pediatric lung transplantation. Low Ig levels are associated with increased infections and hospital stay.