Bromotrifluoromethane (CBrF 3) would have considerable potential as a closed environment fire extinguishing agent, except for its membership in that large group of hydrocarbons capable of precipitating irregular heart action when inhaled by persons with elevated levels of blood epinephrine. These experiments were an effort to determine whether myocardial glycolysis was impaired in male Wistar rats breathing 79 21 CBrF 3 O 2 and challenged with 1-epinephrine in what would ordinarily constitute subtoxic doses. CNS effects were the major observations in rats exposed to both CBrF 3 and epinephrine; 17 of the 20 rats so exposed suffered respiratory arrest within 40 min, and several of them exhibited erratic, convulsive behavior prior to exhibiting respiratory difficulties. All control rats survived, and myocardial levels of glycolytic intermediates were compared in animals breathing air or CBrF 3 O 2 , with and without epinephrine challenge, using “crossover plots.” With air-epinephrine and CBrF 3-epinephrine there were crossovers (activation) at phosphofructokinase, and the general picture was consistent with the CBrF 3 induction of respiratory depression and hypoxia, resulting in the mobilization and intracellular accumulation of free fatty acids.