Oxygen binding properties of fifteen kinds of abnormal hemoglobins discovered in Japan were elucidated with the automatic oxygenation apparatus which was developed by Imai et al. This paper reviews the functional characteristics of those hemoglobins previously reported, presents functional data of some newly studied hemoglobins, and gives a discussion on structure-function relationships in those hemoglobins. This paper also describes a simple procedure for generating a predicted oxygen equilibrium curve of non-isolatable hemoglobin from equilibrium curves of normal hemolysate and hemolysate containing that hemoglobin.