Chronic sinusitis is frequently associated with chronic lower respiratory tract diseases, and the association is referred to as sinobronchial syndrome (SBS). This study was carried out to determine the incidence of otitis media with effusion in the patients with sinobronchial syndrome and to investigate the efficacy of low-dose and long-term erythromycin therapy for otitis media with effusion associated with sinobronchial syndrome. We have found a high incidence of otitis media with effusion in patients with sinobronchial syndrome, the morbidity rate being 54% in 50 cases studied. This ear disease seems to be the major cause of hearing disturbance in patients with sinobronchial syndrome. Sixteen patients with both sinobronchial syndrome and otitis media with effusion were given low-dose and long-term erythromycin therapy (erythromycin base, 600 mg/d for more than 4 months); of these, 13 became effusion-free and most subjects showed improvement in the symptoms of sinobronchial syndrome. The erythromycin therapy thus seems to be exceedingly effective for the treatment of sinobronchial syndrome and associated otitis media with effusion.