This clinical practice guideline formulates recommendations for health care providers regarding the diagnosis, evaluation, and treatment of children, ages 1 to 21 years, with uncomplicated acute, subacute, and recurrent acute bacterial sinusitis. It was developed through a comprehensive search and analysis of the medical literature. Expert consensus opinion was used to enhance or formulate recommendations where data were insufficient. A subcommittee, composed of pediatricians with expertise in infectious disease, allergy, epidemiology, family practice, and pediatric practice, supplemented with an otolaryngologist and radiologist, were selected to formulate the practice parameter. Several other groups (including members of the American College of Emergency Physicians, American Academy of Otolaryngology-Head and Neck Surgery, American Academy of Asthma, Allergy and Immunology, as well as numerous national committees and sections of the American Academy of Pediatrics) have reviewed and revised the guideline. Three specific issues were considered: 1) evidence for the efficacy of various antibiotics in children; 2) evidence for the efficacy of various ancillary, nonantibiotic regimens; and 3) the diagnostic accuracy and concordance of clinical symptoms, radiography (and other imaging methods), and sinus aspiration. It is recommended that the diagnosis of acute bacterial sinusitis be based on clinical criteria in children 6 years of age. Computed tomography scans of the paranasal sinuses should be reserved for children who present with complications of acute bacterial sinusitis or who have very persistent or recurrent infections and are not responsive to medical management. There were only 5 controlled randomized trials and 8 case series on antimicrobial therapy for acute bacterial sinusitis in children. However, these data, plus data derived from the study of adults with acute bacterial sinusitis, support the recommendation that acute bacterial sinusitis be treated with antimicrobial therapy to achieve a more rapid clinical cure. Children with complications or suspected complications of acute bacterial sinusitis should be treated promptly and aggressively with antibiotics and, when appropriate, drainage. Based on controversial and limited data, no recommendations are made about the use of prophylactic antimicrobials, ancillary therapies, or complementary/alternative medicine for prevention and treatment of acute bacterial sinusitis. This clinical practice guideline is not intended as a sole source of guidance in the diagnosis and management of acute bacterial sinusitis in children. It is designed to assist pediatricians by providing an analytic framework for evaluation and treatment. It is not intended to replace clinical judgment or establish a protocol for all patients with this condition.