The purpose of this study was to define the incidence and type of pulmonary complications experienced by children after orthotopic liver transplantation (OLT). The radiological records of all patients receiving OLT during a 3-yr period were reviewed to identify evidence of a pulmonary abnormality. Medical records were then reviewed to determine type, duration, therapy and outcome of pulmonary disorders. Potential risk factors for the development of persistent pleural effusions were also analyzed. One hundred and fifty-one pediatric liver transplantations were performed on 113 patients during this period. Pneumonia developed in 27 patients, including 11 proven bacterial, six presumed bacterial, six viral and four fungal cases. All three deaths related to pulmonary complications were in this group. Three patients developed mild pulmonary hemorrhages, and three developed pulmonary calcifications, which did not impair lung function. Sixteen patients developed paralysis of the right hemidiaphragm, four required diaphragm plication. Pleural effusions developed in 86 patients, 38 persisted longer than 7 days. Patients with persistent effusions were more likely to develop allograft rejection than patients with no persistent effusion (p < 0.01) by chi2 analysis. Seven patients required tracheostomy placement. Of these, four were successfully decannulated, two died from non-pulmonary complications and one is receiving home ventilator support. In conclusion, the majority of children experience at least one pulmonary complication after OLT, but mortality due to pulmonary disease is low in this population. Persistent pleural effusions may be a heralding sign of allograft rejection. Viral, bacterial and fungal pneumonia were the only pulmonary causes of death and only one patient in this series has had significant chronic lung disease.