The American Academy of Otolaryngology and other authorities have recommended the use the of term rhinosinusitis instead of sinusitis because infection of the paranasal sinuses almost always occurs with, or as a complication of, viral rhinitis. Uncommonly, infection in a paranasal sinus without preceding viral upper respiratory infection can result from the prolonged presence of a nasogastric or endotracheal tube or nasal packing in a nostril or from dental infections or procedures. Some 16% of the U.S. population reports a diagnosis of sinusitis annually, and 16 million physician visits are made each year because of this condition. The mechanism whereby viral upper respiratory infection (URI) leads to rhinosinusitis includes obstruction of sinus ostia as a result of mucosal edema, stagnation of mucus due to increased mucus production, and impairment of ciliary activity caused by local inflammation, and faulty aeration of sinuses with resulting reduction in oxygen tension. Factors that are known or believed to increase the likelihood that rhinosinusitis will develop as a complication of acute viral URI include cigarette smoking; chronic allergic rhinitis, particularly with polyp formation; use of over-the-counter products containing first-generation antihistamines, which thwart the mucus transport system by drying nasal mucus and inhibiting ciliary action; abuse of decongestant nose drops or sprays, which can induce rebound nasal congestion, rhinitis medicamentosa, or both; and any anatomic abnormality that interferes with normal drainage and aeration of the sinuses. Septal deviation is the most widely recognized anatomic factor. Congenital narrowness of the middle meatus, into which the ostia of the frontal, maxillary, and anterior ethmoid sinuses drain, can predispose to sinus obstruction as a consequence of even slight nasal congestion. This condition has been called ostiomeatal complex. Most cases of acute rhinosinusitis are caused by viruses and are self-limited, resolving in 10-14 days with or without treatment. Although it is estimated that only 0.5%-2% of cases of acute rhinosinusitis are bacterial in origin, rhinosinusitis is the fifth most common condition for which antibiotics are prescribed, and the most common of all in ambulatory practice. One explanation for this lies in the inappropriate expectations and demands of a misinformed public. Nearly 50% of people surveyed believe that colds are caused by bacteria and can be cured with antibiotics. In addition, those with a history of recurrent rhinosinusitis often seek treatment early in the course of a common cold and are treated "expectantly" or "prophylactically" with antibiotics. Another reason for the widespread overuse of antibiotics to treat rhinosinusitis is that valid clinical diagnostic criteria to identify rhinosinusitis and to distinguish acute bacterial rhinosinusitis from viral infection are not available. Fever, green nasal discharge, a sense of pressure (not pain) in maxillary and frontal areas, and tenderness to palpation over these areas are all features of undifferentiated viral URI. Individual signs and symptoms that have been widely regarded by both physicians and laity as indicative of bacterial rhinosinusitis, such as maxillary pain, dental pain, purulent (white or off-white) nasal discharge, prolongation of nasal obstruction for more than 1 week, failure of obstruction to respond to oral decongestant, and biphasic illness (rhinitis beginning to improve and then relapsing) actually have little diagnostic value, although the occurrence of several of these together has a certain cumulative weight. Detection of purulent drainage from sinus ostia on rhinoscopy certainly suggests bacterial rhinosinusitis, but other diagnostic maneuvers are seldom useful in clinical practice; transillumination of the maxillary and frontal sinuses is of dubious value, imaging studies (plain x-rays and CT scan) are not cost effective, culture of nasal secretions reflects the mixed flora of the nose rather than pathogens within paranasal sinuses, and sinus puncture to obtain material for culture is painful. Acute bacterial rhinosinusitis is typically due to a single pathogen. The organisms most often cultured are Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis, Staphylococcus aureus, and anaerobes. Measures available for the treatment of rhinosinusitis are far from satisfactory. Oral decongestants and analgesics may help to allay symptoms. In selected cases, a brief course of a topical decongestant or oral corticosteroid may favorably affect the outcome. Nonsedating antihistamines, topical corticosteroids, or both are indicated when allergic rhinitis is a contributing factor. First-generation antihistamines, contained in many over-the-counter sinus and nighttime cold remedies, are contraindicated. Antibiotics favored for the treatment of acute bacterial rhinosinusitis are amoxicillin with or without clavulanate, trimethoprim-sulfamethoxazole, doxycycline, and various cephalosporins, macrolides, and fluoroquinolones. However, randomized clinical trials have failed to show that antibiotics consistently affect the course of acute rhinosinusitis, even when a bacterial cause has been demonstrated. More than 10% of the U.S. population suffers subacute (4-12 weeks) or chronic (longer than 12 weeks) rhinosinusitis each year. Physicians regularly prescribe antibiotic treatment for chronic rhinosinusitis, even though no study of the efficacy of such treatment in adults has been published in more than a generation, and placebo-controlled studies in children have failed to show any beneficial effect of antibiotics on either short-term or long-term outcome. Symptoms may be nonspecific, and allergic or vasomotor rhinitis may coexist with chronic bacterial infection. A surgical procedure to establish temporary or permanent artificial drainage of one or more sinus cavities is indicated for severe, intractable chronic rhinosinusitis and for disease complicated by extranasal spread of infection or by mucocele or pyocele. Grave complications of bacterial rhinosinusitis are orbital cellulitis, subperiosteal orbital abscess, osteomyelitis of the frontal bone (Pott puffy tumor), superior sagittal sinus thrombosis, and subdural, epidural, or intracerebral abscess.