Rhinosinusitis is defined as inflammation of one or more of the paranasal sinuses and affects approximately 12% of the population. Acute rhinosinusitis is defined as symptoms that last < 12 weeks, and chronic rhinosinusitis (CRS) is defined as symptoms that last > 12 weeks. CRS is divided into three groups: CRS with nasal polyps (CRSwNP), CRS without nasal polyps (CRSsNP), and allergic fungal rhinosinusitis. Nasal polyps are inflammatory outgrowths of paranasal sinus mucosa caused by chronic mucosal inflammation and are present in 20% of patients with CRS. Nasal polyps typically present with nasal congestion, nasal obstruction, and anosmia or hyposmia, and occur more frequently in patients with persistent asthma, aspirin-exacerbated respiratory disease (AERD), CRS, and cystic fibrosis. The sinus cavities are lined with pseudostratified ciliated columnar epithelial cells interspersed with mucous goblet cells. Cilia continuously sweep the mucous toward the ostial openings and are important in maintaining the proper environment of the sinus cavities. The frontal, maxillary, and anterior ethmoid sinuses drain into the ostiomeatal unit of the middle meatus. The posterior ethmoid sinuses and superior sphenoid sinuses drain into the sphenoethmoid recess of the superior meatus. Most acute sinus infections are caused by viruses, and, therefore, it is not surprising that the majority of patients improve within 2 weeks without antibiotic treatment. A bacterial infection should be considered if symptoms worsen or fail to improve within 7-10 days. Combining an intranasal corticosteroid with an antibiotic reduces symptoms more effectively than antibiotics alone. Topical nasal steroids are the treatment of choice for nasal polyps. They significantly decrease polyp size, nasal congestion, and rhinorrhea, and increase nasal airflow. Short courses of oral steroids may be needed to reduce polyp size, followed by maintenance therapy with topical steroids. Surgery is reserved for patients in which polyps cause severe obstruction or recurrent sinusitis and for patients for whom medical therapy has failed. Aspirin desensitization may decrease the requirement for polypectomies and sinus surgery in patients with AERD.