The diagnosis of Burkitt lymphoma by thoracentesis has been rarely reported in the literature, particularly in children. From 1995 to 2004, we diagnosed six pediatric patients with mature B-cell neoplasms using thoracentesis as the initial diagnostic procedure. The cytology, immunophenotyping, and cytogenetic results of the pleural fluid cells were consistent with mature B-cell malignancies. We conclude that thoracentesis for the diagnosis of Burkitt lymphoma in children is safe, fast, and accurate. It should be strongly considered as an initial diagnostic procedure for pediatric patients with pleural effusions who are suspected of having B-cell malignancies.