The effects of external low-Ca, high-Mg solutions were tested both on frog isolated semicircular canals and on single cells isolated from these sensory organs. Our results showed that these media were able to cancel slow adaptation of the ampullar microphonic current in the whole organ and to abolish a Ca-dependent K current (IK(Ca)) in single hair cells, suggesting that IK(Ca) is involved in vestibular sensory adaptation.