Sinusitis is a very common and increasingly recognized disorder affecting patients of all ages and genders. It is most commonly due to infection of the paranasal sinuses with symptoms varying from cough and anterior nasal drainage in children to headache and post nasal drip in adults. Diagnosis relies heavily on medical history with corroboration by careful physical examination including nasal endoscopy. The most accurate imaging technique to evaluate sinusitis and to delineate the extent of involvement of individual sinuses and identify possible anatomic abnormalities is computerized tomography scanning in the coronal plane. The mainstay of medical treatment of sinusitis is antibiotics with adjuvant treatments such as saline irrigation, decongestants, mucolytics and antiinflammatory agents playing a more secondary role. The use of these agents will be discussed in detail after an introduction about the risk factors, diagnosis and bacteriology of the disease. Surgical treatment of sinusitis will be the subject of another article.