Round window membrane ruptures and perilymph fistula can present the complication of sudden deafness and symptoms of vertigo, tinnitus, and sensorineural hearing loss. The round window fistula was experimentally created in rabbits. The head tilt, postural change, and spontaneous nystagmus were observed with time intervals of 6, 12, 24, 36, 48th hr after formation of the fistula. 1 Head tilt and postural change. On 6th hr after formation of the fistula, head tilt and postural change toward the operated side were observed in 8 cases. They remained continuously until 12th hr after formation of the fistula. They disappeared after 36th hr in 4 cases and after 48th hr in 4 cases. 2 Spontaneous nystagmus. On 6th hr after formation of the fistula, the spontaneous nystagmus with 115/min of average frequency toward opposite side was observed in 8 cases. It remained continuously until 12th hr after formation of the fistula. In 7 cases, amplitude increased and frequency decreased after 24th hr After 36th hr the spontaneous nystagmus disappeared in 4 cases and amplitude decreased in 4 cases. The spontaneous nystagmus disappeared after 48th hr in all cases.