Unilateral tubal occlusion was performed in 10 cats, which were sacrificed 26-44 months later. During the observation period repeated bilateral tympanometry and auditory nerve response were recorded. Paracentesis with evacuation of effusion was performed up to eight times and the effusion was examined by viscometry. After sacrifice, quantitative histopathology of the bulla with determination of goblet cell density was carried out. In three ears having glue at the last paracentesis, the histopathologic changes were more pronounced than in the four ears having thin effusion. Three ears were dry at sacrifice with normal tympanometry, the histopathological changes evidently demonstrate the the normalization of the middle ear mucosa. The experiments demonstrate the great importance of tubal patency or function in prognosis of the disease. In ears with anatomically occluded tubes, no recovery occurred, whereas in ears with normalized tubal function, the middle ear mucosa and goblet cell density also normalized. Pathogenic and etiological aspects of secretory otitis are discussed.