Transcatheter closure of a patent ductus arteriosus (PDA) is a well-established technique that may occasionally be complicated by severe thrombocytopenia. We report herein 6 cases of PDA in which circulating platelet counts were notably reduced within 18-48 hours following the procedure. A number of interventions, including blood-pressure control, protection against hemorrhage, and eradication of residual flow, were performed. Platelet counts in all patients were restored to preprocedural levels through intravenous infusion of dexamethasone and human gamma globulin.