['Pneumocystis carinii pneumonia (PCP) is a potentially life-threatening but preventable infection that may occur after hematopoietic stem cell transplantation (HSCT). Intravenous pentamidine has been used in the prevention of PCP in the post-transplant period, although there are few trials published in the literature evaluating its safety and efficacy.', 'We retrospectively reviewed the medical records of children who underwent HSCT from January 1, 2005, to October 1, 2011, who received intravenous pentamidine as first-line PCP prophylaxis initiated at admission. Demographic, clinical, microbiologic, management and outcome data were collected.', 'One hundred sixty-seven consecutive HSCTs in 137 pediatric patients were given intravenous pentamidine before myeloablation and then every 28 days until the subject was at least a minimum 30 days post-HSCT, had stable neutrophil engraftment (absolute neutrophil count >1000/mm for 3 days without growth factor support) and for allogeneic patients, no evidence of active graft versus host disease and weaning on their immunosuppressive therapy. No cases of PCP were seen in this cohort. Ten (7%) had a grade I side effect of nausea/vomiting requiring slower infusion time and 2 (2%) had a grade IV reaction with anaphylaxis (rash) and hypotension with 1 child requiring transfer to the intensive care unit.'] Is intravenous pentamidine safe and effective as primary pneumocystis pneumonia prophylaxis in children and adolescents undergoing hematopoietic stem cell transplantation?