Inhibitors of mitochondrial function have been known to be stimulants of the carotid body for many decades. Recent experiments have demonstrated that in isolated neonatal rat type I cells both hypoxia and mitochondrial uncouplers inhibit background K+ currents. This leads to membrane depolarisation and voltage gated Ca2+ entry (Buckler, 1997; Buckler and Vaughan-Jones, 1998). Since these data are consistent with a role for mitochondria in oxygen sensing, we have determined whether other mitochondrial inhibitors mimic the effects of hypoxia on the type I cells.