A rat model of otitis media with effusion (OME) was developed by intratympanic injection of E. coli endotoxin and section of the third branch of the trigeminal nerve (V3). The period of fluid retention induced by the endotoxin was prolonged for 5 days or longer, in cases when tubal function was impaired by cutting of V3. Three Eustachian tube function tests (patency test of inflation-deflation tests, forced response test and negative pressure test) were carried out before and after the endotoxin inoculation and V3 sectioning. At 4 days after these procedures, passive opening pressure (Po), closing pressure (Pc) and tubal resistance (R2) were significantly lowered. The negative pressure test showed impaired capacity of active opening. This model of Eustachian tube dysfunction is considered to reveal functional obstruction, a condition similar to that of clinical cases of OME. The study shows that both inflammation in the middle ear and tubal dysfunction, such as functional obstruction, are factors in the development and prolongation of OME.