ABSTRACT. Renal abscess is uncommon in pediatrics and is rarely a cause of fever of unknown origin. We recently cared for a patient who presented with a 3-week history of fever. An indium scan ultimately led to the diagnosis of a renal abscess. Aspiration yielded Peptostreptococcus asaccharolyticus. This unusual case prompted a review of the clinical and microbiologic features of renal abscess in pediatric patients at our hospital over the past 10 years. Seven additional patients with a discharge diagnosis of renal abscess were identified. Only 2 of the patients had identifiable risk factors (diabetes mellitus and polycystic kidneys). Staphylococcus aureus or Enterobacteriaceae were responsible for most infections, consistent with hematogenous and urinary tract sources, respectively. No other cases of anaerobic abscess were identified. This case highlights the importance of considering a renal abscess in the differential diagnosis of fever of unknown origin and of processing specimens for both aerobic and anaerobic organisms. ABBREVIATIONS. FUO, fever of unknown origin; MRI, magnetic resonance imaging; CT, computed tomography; CVA, costovertebral angle.