OBJECTIVE: This guideline provides evidence-based recommendations on managing sinusitis, defined as symptomatic inflammation of the paranasal sinuses. Sinusitis affects 1 in 7 adults in the United States, resulting in about 31 million individuals diagnosed each year. Since sinusitis almost always involves the nasal cavity, the term rhinosinusitis is preferred. The guideline target patient is aged 18 years or older with uncomplicated rhinosinusitis, evaluated in any setting in which an adult with rhinosinusitis would be identified, monitored, or managed. This guideline is intended for all clinicians who are likely to diagnose and manage adults with sinusitis. PURPOSE: The primary purpose of this guideline is to improve diagnostic accuracy for adult rhinosinusitis, reduce inappropriate antibiotic use, reduce inappropriate use of radiographic imaging, and promote appropriate use of ancillary tests that include nasal endoscopy, computed tomography, and testing for allergy and immune function. In creating this guideline the American Academy of Otolaryngology-Head and Neck Surgery Foundation selected a panel representing the fields of allergy, emergency medicine, family medicine, health insurance, immunology, infectious disease, internal medicine, medical informatics, nursing, otolaryngology-head and neck surgery, pulmonology, and radiology. RESULTS: The panel made strong recommendations that 1) clinicians should distinguish presumed acute bacterial rhinosinusitis (ABRS) from acute rhinosinusitis caused by viral upper respiratory infections and noninfectious conditions, and a clinician should diagnose ABRS when (a) symptoms or signs of acute rhinosinusitis are present 10 days or more beyond the onset of upper respiratory symptoms, or (b) symptoms or signs of acute rhinosinusitis worsen within 10 days after an initial improvement (double worsening), and 2) the management of ABRS should include an assessment of pain, with analgesic treatment based on the severity of pain. The panel made a recommendation against radiographic imaging for patients who meet diagnostic criteria for acute rhinosinusitis, unless a complication or alternative diagnosis is suspected. The panel made recommendations that 1) if a decision is made to treat ABRS with an antibiotic agent, the clinician should prescribe amoxicillin as first-line therapy for most adults, 2) if the patient worsens or fails to improve with the initial management option by 7 days, the clinician should reassess the patient to confirm ABRS, exclude other causes of illness, and detect complications, 3) clinicians should distinguish chronic rhinosinusitis (CRS) and recurrent acute rhinosinusitis from isolated episodes of ABRS and other causes of sinonasal symptoms, 4) clinicians should assess the patient with CRS or recurrent acute rhinosinusitis for factors that modify management, such as allergic rhinitis, cystic fibrosis, immunocompromised state, ciliary dyskinesia, and anatomic variation, 5) the clinician should corroborate a diagnosis and/or investigate for underlying causes of CRS and recurrent acute rhinosinusitis, 6) the clinician should obtain computed tomography of the paranasal sinuses in diagnosing or evaluating a patient with CRS or recurrent acute rhinosinusitis, and 7) clinicians should educate/counsel patients with CRS or recurrent acute rhinosinusitis regarding control measures. The panel offered as options that 1) clinicians may prescribe symptomatic relief in managing viral rhinosinusitis, 2) clinicians may prescribe symptomatic relief in managing ABRS, 3) observation without use of antibiotics is an option for selected adults with uncomplicated ABRS who have mild illness (mild pain and temperature <38.3 degrees C or 101 degrees F) and assurance of follow-up, 4) the clinician may obtain nasal endoscopy in diagnosing or evaluating a patient with CRS or recurrent acute rhinosinusitis, and 5) the clinician may obtain testing for allergy and immune function in evaluating a patient with CRS or recurrent acute rhinosinusitis. DISCLAIMER: This clinical practice guideline is not intended as a sole source of guidance for managing adults with rhinosinusitis. Rather, it is designed to assist clinicians by providing an evidence-based framework for decision-making strategies. It is not intended to replace clinical judgment or establish a protocol for all individuals with this condition, and may not provide the only appropriate approach to diagnosing and managing this problem.