The administration of "sweet spirits of nitre" (4% ethyl nitrite CH3CH2ONO in 70% ethyl alcohol) was followed by acute methemoglobinemia and severe anoxic metabolic acidosis in infant twins, Methylene blue administration reversed methemoglobinemia in both, but one twin died from the consequences of hypoxemia. Hemoglobin electrophoresis and methemoglobin reductase determinations were normal for age. This medicine is available without prescription and contains the potent oxidant ethyl nitrite. In infants with sudded death or onset of cyanosis, appropriate toxicological and historical information should be obtained.