Prostaglandins (PG) are naturally occurring, cyclic, unsaturated fatty acids that possess a wide range of potent biologic activities. Prostaglandins have been found in human middle ear effusions and may have implications for understanding the inflammation and, possibly, the bone resorption seen in chronic otitis media. In the study presented, PGs were measured by radioimmuno-assay in middle ear effusions from experimentally induced serous and purulent otitis media Dj C D 14-AUG-80 M 204 T KMA K 11.30 in chinchillas. The ability of chinchilla middle ear mucosa to synthesize PGs from (14C)-arachidonic acid was also demonstrated. The authors suggest an active role for PGs in the inflammation and the bone resorption seen in otitis media.