Nitroglycerin (55630) is reviewed. Nitroglycerin is a colorless, oily liquid that explodes violently from shock or when heated to 260 degrees-C. It is used in the manufacture of dynamite, blasting gelatin, and cordite (12751030), and as a pharmaceutical agent for treatment of angina pectoris. The physical and chemical properties of nitroglycerin are listed as: molecular weight, 227.1; specific gravity, 1.601; melting point, 13 degrees; vapor density, 7.8; vapor pressure, 0.00025 millimeters of mercury at 20 degrees; slight solubility in water and partial solubility in alcohol; and miscibility with ether and chloroform. Physiological responses are discussed; absorption of nitroglycerin occurs through skin, lungs, and mucous membranes. Symptoms of exposure to small amounts include intense, throbbing headache, nausea, vomiting, and abdominal pain; exposure to large amounts results in hypotension, depression, confusion, delirium, methemoglobinemia, and cyanosis. The potentiating effect of alcohol after exposure to nitroglycerin is noted. Medical studies are cited that indicate no permanent deterioration in health. The author concludes that a threshold limit value of 0.5 parts per million is warranted. Headaches and other symptoms occur at that concentration, but chronic injury is unlikely.