Rhinosinusitis is one of the most common health care complaints in this country. The burden on affected individuals in terms of decreased productivity, absenteeism from the workplace, and diminished quality of life, when added to the cost of care and the growing public health menace of antibiotic-resistant bacteria, makes rhinosinusitis a serious disease that warrants precise diagnosis and effective therapy. Technologic innovations in endoscopy and imaging have improved understanding of sinus pathophysiology, but diagnosis remains clinical and treatment empiric. Recognized pitfalls in acute rhinosinusitis management are injudicious use of antibiotics and antihistamines. Chronic rhinosinusitis is a complex, multifactorial disorder, not simply an infectious disease. In many patients, noninfectious inflammation and structural problems play an important role. Medical management should include an intranasal corticosteroid in addition to an appropriate antibiotic. Otolaryngology referral is indicated for complications of acute infection, immunocompromised patients, nasal polyps, and chronic rhinosinusitis having substantial effect on quality of life. Modern surgical principles that focus on obstructive pathology in the OMC region are efficacious but rarely curative. Developments in the fields of immunology, molecular biology, and genetics will lead to more effective treatment options.