Studies of the clinical features of hereditary spherocytosis since 1871 and laboratory investigation of the cellular abnormalities since 1940 have led to the characterization of hereditary spherocytosis as a prime example of a Mendelian dominant, genetically determined disorder of the erythrocyte membrane. This review of hereditary spherocytosis emphasizes the contributions of Dr. Lawrence Young and many others of out present understanding of the disease and discusses current studies of the protein abnormality in the membrane of hereditary spherocytes.