Median corpuscular fragility of erythrocytes does not differ significantly between fed and fasted Bolivian and Brazilian squirrel monkeys and are similar to values reported in humans and rhesus monkeys. This report further confirms that the fasting hyperbilirubinemia present only in Bolivian squirrel monkeys with a Gilbert-like syndrome is not due to an increased fragility of erythrocytes and should be classified as a nonhemolytic hyperbilirubinemia.