Gene analysis in Japanese patients with congenital hemolytic anemia due to red cell membrane disorders, thalassemias, unstable hemoglobinopathies and red cell enzymopathies were summarized. In hereditary spherocytosis, twenty-four mutations of band 3, five mutations of protein 4.2 and twenty mutations of ankyrin have been identified. In beta thalassemia, fourty-seven mutations of beta globin have been found, and ten mutations among them comprise 80% of beta thalassemia patients in Japan. Most common alpha0 and alpha+ thalassemia are--SEA and--alpha3.7, respectively. Fourty glucose-6-phosphate dehydrogenase mutations and twenty-three pyruvate kinase mutations have been identified, allowing a better understanding of the structure-function relationships of these enzymes.