A 16 years old boy had a typical exertional hemoglobinuria after walking with his new leather shoes on. The attacks of hemoglobinuria were associated with the appearance of an unstable hemoglobin in red cells. A slightly decreased fragility curve by 24 hr incubated red cells, the increase of autohemolysis and the appearance of heat labile hemoglobin were observed after exertion. These findings support that exertional hemoglobinuria may be regarded as a transitory erythropathia.