Various host factors and infectious agents have been implicated in the genesis of AOM and SOM. Host factors include anatomical or physiological Eustachian tube dysfunction, retrograde movement of organisms from the nasopharynx, allergy, and exposure to environmental irritants, and ciliary dysfunction. Bacterial and viral organisms are recognized as a common cause of otitis media. In a small but significant number of cases, there is failure of resolution despite optimal medical therapy to address presumed host factors and infectious agents. In these cases, routine bacterial and viral cultures can be negative suggesting the presence of other pathogens. Routine bacterial and viral cultures of middle ear fluid are often negative, suggesting that other infectious agents may be involved. Because of the similarities between the paranasal sinuses and middle ear space and the recent recognition of fungi as important pathogens in inflammation of the paranasal sinuses, the fungi can play role in serous otitis media. Fungi can interact and influence the upper respiratory tract in various fashions.