A retrospective review of adenoviral infection in pediatric liver transplant recipients was done at Children's Hospital of Pittsburgh to define its epidemiology and clinical importance. Medical records of patients with adenovirus were reviewed and data collected regarding clinical course, microbiologic studies, biopsy results, immunosuppression, concurrent infections, and outcome. Of 484 liver transplant recipients, 49 had 53 episodes of adenoviral infection. The most common sites of adenoviral infection were the liver, lung, and gastrointestinal tract. Serotypes 1, 2, and 5 were recovered most often; type 5 was commonly associated with hepatitis. Invasive adenoviral infection occurred in 20 children, leading to death in 9. Median time from transplantation until isolation of adenovirus was 25.5 days. This timing suggests either reactivation or donor-associated transmission. Prospective studies using molecular epidemiologic techniques will be helpful in evaluating transmission patterns of adenovirus in this population.