Heredity, viral infection, and head or acoustic trauma are considered the common etiologies for a unilateral sensorineural deafness in children. The incidence of perilymphatic fistula in a unilateral hearing loss is still unknown. Inner ear-related symptoms in children are scarce, and little diagnostic laboratory testing is available. A definite diagnosis of a perilymphatic fistula can therefore be made only by an exploratory tympanotomy. Four children, ages 5 to 15 years, with a history of a recent and rapidly progressive unilateral sensorineural hearing loss, were explored. Preoperative laboratory data, which included a fistula test, ENG, CT scan of the temporal bones, and an ABR, were all within normal limits. An overt fistula was found in only one of the patients. Only an exploratory tympanotomy can arrest and possibly reverse a unilateral hearing loss or discontinue a middle ear-cranial cavity communication. It is therefore our feeling that, in patients with an appropriate history, the potential benefit outweighs the risk and morbidity of an exploratory tympanotomy.