OBJECTIVE To test the efficacy of occlusion of the enlarged vestibular aqueduct to treat the progressive sensorineural hearing loss associated with the enlarged vestibular aqueduct (EVA) syndrome. METHODS Prospective controlled study. METHODS Tertiary care referral center. METHODS Sixteen consecutive patients (29 affected ears) with progressive sensorineural hearing loss and vestibular aqueducts >1.5 mm in diameter without other inner ear anomalies participated in this study. METHODS In 10 patients with progressive hearing loss, the EVA was occluded in the ear with worse hearing by placing a fascia graft between the posterior fossa dura overlying the endolymphatic sac and intraosseous duct and the posterior semicircular canal without opening the endolymphatic sac. In the operative ears, serial postoperative audiograms were compared with the contralateral ear in patients with bilateral EVA and with the other nonoperated control ears. METHODS The rate of decline of pure-tone average and speech discrimination before surgery in the operated ear was compared with the rate of decline postoperatively in the same ear. The rates of decline in the nonoperated contralateral ear from the same patient and the nonoperated control ears from other patients were also used for comparison with the postoperative rate of decline in the operated ears. RESULTS There was no statistically significant change in the rate of hearing loss in patients undergoing occlusion of the EVA. CONCLUSIONS Extraluminal soft-tissue occlusion of the EVA appears to be a safe procedure but has not yet been shown to be significantly effective in altering the sensorineural hearing loss accompanying the EVA syndrome. Further surgical intervention does not appear warranted until such time that longitudinal follow-up shows sufficient evidence of efficacy of the procedure.