To clarify the role of habitual sniffing caused by nasal diseases in the pathogenesis of middle ear diseases, 112 pediatric patients with secretory otitis media (183 ears) were examined for associated nasal diseases and habitual sniffing. Middle ear pressure and nasopharyngeal pressure were simultaneously measured during forceful sniffing. Fifty-four percent of the patients with secretory otitis media had allergic rhinitis and/or chronic sinusitis. Sixty percent of the patients with nasal diseases habitually sniffed, whereas only 30.8% of those without nasal diseases had this habit. In the patients with the habit of sniffing, a higher negative pressure tended to be created in the nasopharynx on forceful sniffing than in the patients who did not sniff. Thirty-one of 112 patients (27.7%) were positive on the sniff test. Of these 31 patients, 20 were associated with the habit of sniffing, and in 14 of the 20 patients, nasal diseases were considered to be the primary cause of the habit of sniffing. That is, in 14 of the 112 patients (12.5%) with secretory otitis media, the patients with nasal diseases frequently sniffed and their middle ears were evacuated. This study suggests that in many patients, sniffing provoked by nasal diseases plays an important role in the pathogenesis of secretory otitis media through the creation of negative nasopharyngeal pressure. This mechanism is presumed to be present in approximately one-tenth of pediatric patients with secretory otitis media.