Glucagon is an important therapeutic agent in critical care medicine. Although its endogenous hormonal functions have been well described, its clinical uses are rarely discussed. Glucagon is effective in the treatment of hypoglycemia, cardiogenic shock and heart failure, propranolol overdose, esophageal meat impaction, ureteral colic due to calculi, and acute diverticulitis. It may prove useful in the treatment of endotoxin and hypovolemic shock as well as toxicity due to excesses of procainamide, quinidine, or ouabain.