Rhinitis and sinusitis are among the most common medical conditions and are frequently associated. In Western societies an estimated 10% to 25% of the population have allergic rhinitis, with 30 to 60 million persons being affected annually in the United States. It is estimated that sinusitis affects 31 million patients annually in the United States. Both rhinitis and sinusitis can significantly decrease quality of life, aggravate comorbid conditions, and require significant direct medical expenditures. Both conditions also create even greater indirect costs to society by causing lost work and school days and reduced workplace productivity and school learning. Management of allergic rhinitis involves avoidance, many pharmacologic options, and, in appropriately selected patients, allergen immunotherapy. Various types of nonallergic rhinitis are treated with avoidance measures and a more limited repertoire of medications. For purposes of this review, sinusitis and rhinosinusitis are synonymous terms. An acute upper respiratory illness of less than approximately 7 days’ duration is most commonly caused by viral illness (viral rhinosinusitis), whereas acute bacterial sinusitis becomes more likely beyond 7 to 10 days. Although the mainstay of management of acute bacterial sinusitis is antibiotics, treatment of chronic sinusitis is less straightforward because only some chronic sinusitis cases have an infectious basis. Chronic rhinosinusitis (CRS) has been subdivided into 3 types, namely CRS without nasal polyps, CRS with nasal polyps, and allergic fungal rhinosinusitis. Depending on the type of CRS present, a variety of medical and surgical approaches might be required.