Glucose phosphate isomerase (GPI) deficiency is an unusual cause of hereditary nonspherocytic hemolytic anemia described in Israel in 2 families of Arab ancestry. The disease, inherited as an autosomal recessive disorder, manifests itself by symptoms and signs of chronic hemolysis which are often ameliorated by splenectomy. A variety of defective GPI variants, characterized by modified physicochemical and/or kinetic properties of the enzyme have been reported, suggesting extensive polymorphism for this enzyme deficiency. We recently diagnosed GPI deficiency in a 23-year-old Jewish Ashkenazi man. Since the age of 1 year, when a diagnosis of hemolytic anemia of undetermined etiology was made, he has required frequent blood transfusion. Since splenectomy, performed when he was 6 years old, the requirement for blood transfusions diminished drastically, restricted to hemolytic crises following intercurrent febrile illnesses. To the best of our knowledge, this is the first report of GPI deficiency in an Israeli family of Ashkenazi-Russian origin.