Acute hemolytic anemia is associated with a deficiency in glucose 6-phosphate dehydrogenase (G6PD), an X-linked inheritable characteristic. Hemolytic anemia is thought to be caused by a depletion of glutathione and other reducing compounds in red blood cells. Dr. Amoruso and colleagues sought to experimentally test the Calabrese hypothesis, which suggests that G6PD-deficient individuals may be at an increased risk of hemolysis during exposure to low levels of oxidants such as ozone.