ATP-sensitive potassium (K(ATP)) channels are present in many tissues, including pancreatic beta-cells, heart, skeletal muscle, vascular smooth muscle and brain, in which they couple the cell metabolic state to membrane potential. K(ATP) channels are hetero-octameric proteins composed of the pore-forming subunits Kir6.x (Kir6.1 or Kir6.2) of the inwardly rectifying K(+) channel family and the regulatory subunits SURx (SUR1, SUR2A or SUR2B), the receptor of the sulphonylureas widely used in treatment of type 2 diabetes mellitus. Different combinations of Kir6.x and SURx comprise K(ATP) channels with distinct electrophysiological and pharmacological properties, but their physiological functions in the various tissues are unclear. Our studies of Kir6.2 null (knockout) and Kir6.1 null mice have shown that K(ATP) channels are critical metabolic sensors in protection against acute metabolic stress such as hyperglycaemia, hypoglycaemia, ischaemia and hypoxia.