Context: Bacterial infections of the paranasal sinuses are an important cause of morbidity in children. However, these infections may be difficult to distinguish from viral upper respiratory infections. Consequently, children with viral upper respiratory infections are frequently treated with antibiotics. The inappropriate use of antibiotics for viral upper respiratory infections is costly and has been responsible, at least in part, for the emergence of antibiotic resistance. To improve the diagnosis and treatment of patients with acute bacterial sinusitis and reduce the inappropriate use of antibiotics, clinical guidelines have been developed. Three national organizations have recently published different guidelines for the diagnosis and treatment of acute bacterial sinusitis: the American Academy of Pediatrics, the Sinus and Allergy Health Partnership and the Centers for Disease Control and Prevention. All three guidelines recommend that the diagnosis and treatment of acute bacterial sinusitis should be based on clinical criteria without the confirmation of imaging or other laboratory data. Although the similarity between the different guidelines suggests that there is widespread consensus to use clinical criteria to diagnose acute bacterial sinusitis, there is virtually no evidence to support this position.