Here we report the identification and characterization of a novel ENU-induced mutation in Ank1 named hema6. Both heterozygous and homozygous animals exhibit characteristic features of hereditary spherocytosis, such as increased RBC counts, low RBC mean corpuscular volume (MCV), increased osmotic fragility, and shortened life span of RBCs in vivo. This evidence concerns the gene ANK1 and hereditary spherocytosis.