A high tension of oxygen can block the respiratory gasp reaction to intravenous cyanide in man; it can partially reverse electrocardiographic anoxic changes of a dog poisoned by cyanide; it can protect goldfish from lethal doses of this histotoxic agent. The protective effect of oxygen against lethal doses of cyanide on dogs and rabbits has also been reported by other workers. These facts demonstrate conclusively that oxygen is of paramount importance in the immediate treatment of cyanide poisoning. A plea is made that workers with chronic cerebral, cardiac, or pulmonary disease be excluded from handling cyanide products. Oxygen, sodium nitrite, and thiosulfate in combination are believed to represent the best present-day therapy of cyanide intoxication.