Autooxidation reaction parameters for human, ram, ox, polar fox and sturgeon haemoglobins have been studied by their spectral properties and compared to oxygen affinity of haemoglobins and thermohemolytic resistance of erythrocytes with the aim to ascertain the earlier revealed interrelation between the affinity and thermoresistance. Qualitative correspondence of haemoglobin autooxidability and erythrocyte haemolytic resistance has been shown. Vertebrates with higher haemoglobin autooxidation rate (human, polar fox, sturgeon) have erythrocytes of sufficiently less resistance as compared to ram and ox red blood cells that contain haemoglobin with a lesser autooxidation rate. The results obtained suggest that the haemoglobins with higher oxygen affinity are characterized by increased autooxidability, which causes the reduction of haemolytic resistance due to free-radical processes.