The syndrome of malignant hyperthermia (MHS) has been visualized from the point at which sarcoplasmic Ca 2+ concentration becomes sufficient to stimulate phosphorylase kinase and, indirectly, myosin ATPase. Elevated lv 2+ e els of cellular Ca may cause a functional uncoupling of oxidative phosphorylation as the mitochondria utilize high energy intermediates to sequester Ca 2+. Consequently, ATP is consumed, and the cellular levels of ADP and inorganic phosphorus increases, further stimulating glycolysis as the MHS develops. As the mitochondria sequester Ca 2+, 02 consumption is increased and this, in addition to the stimulating effect of temperature, may explain the observed increase in O2 consumption.However, the triggering mechanisms that allow the various body functions, when exposed to halothane, to combine in an abnormal manner to produce what we recognize as malignant hyperthermia remain obscure. (