Of seven patients with hydrops confirmed by MRI before surgery, both cochlear and vestibular hydrops became negative in two, cochlear hydrops became negative in one, both hydrops were present, but reduced, in one, and there was no change in three patients. The number of vertigo spells was reduced in all cases at 6-12 months after surgery. As for the three cases of negative hydrops, vertigo was completely suppressed. In two cases in which hearing level improved, hydrops became negative after surgery.