In the squirrel monkey noninflammatory mechanical obstruction of the eustachian tube results in the collection of a clear straw-colored, nonpurulent fluid in the tympanum. At the present time it is presumed that the fluid collection is the direct result of mechanical obstruction of the tube, although this was demonstrated histologically in only two out of 13 animals. The alternative possibility is lymphatic obstruction. It is significant that 93% of the animals developed a clear fluid which has the characteristics of a transudate. In clinical medicine one finds different types of middle ear effusions, all of which are labeled generically as serous otitis media. As it has been possible in this experiment to produce, with a simple technique, the same type of noninflammatory fluid in 93% of our animals, it is believed that this represents the creation of a reliable experimental model which can be used for further investigations into the etiology of the other generic forms of serous otitis media.