The diagnosis and management of perilymphatic fistula has received considerable attention in recent years. Despite the use of sophisticated technology, the diagnosis of perilymphatic fistula continues to rest primarily upon clinical suspicion and the exclusion of other disorders. In addition, the confirmation of a perilymphatic fistula during surgical exploration is usually based upon the subjective observation of fluid pooling in niches of the middle ear. A sensitive and objective laboratory test for identifying perilymph in the middle ear would be a useful adjunct for the diagnosis and management of perilymphatic fistula. The objective of this paper is to demonstrate the potential utility of beta 2 (beta 2) transferrin assay in the diagnosis of perilymphatic fistula. To accomplish this objective, we confirmed that beta 2 transferrin is present in living human perilymph and is absent in the normal or inflamed middle ear. In addition, the utility of beta 2 transferrin assay in the diagnosis of cerebrospinal fluid otorrhea is presented.