A new glucose-6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was reported. The patient, a 6-year-old Japanese male, was noticed to have hemolytic anemia soon after birth, and a diagnosis of G6PD deficiency was made at the age of 2. He had episodes of hemolytic crisis several times after upper respiratory infection. G6PD activity of the patient was 5.5% of normal. The enzymatic characteristics were examined when he was 5 years old, and his G6PD showed faster-than-normal electrophoretic mobility, low Km G6P, high Km NADP, low Ki NADPH, normal utilization of substrate analogues, heat instability, and a normal pH optimum curve. From these results, this was considered to be a new variant and was designated G6PD Nagano. Infection-induced hemolysis and chronic hemolytic anemia seem to be due to markedly impaired enzyme activity and thermal instability.