Hereditary spherocytosis (HS) is a common inherited erythrocyte membrane disorder characterized by chronic hemolytic anemia. Clinical manifestations and biochemical abnormalities of HS are heterogeneous. In this study, we investigated erythrocyte membrane protein defects in 27 Korean HS cases. Utilizing both the Fairbanks system and the Laemmli system, sodium dodecyl sulfate polyacrylamide gel electrophoresis of erythrocyte membrane proteins was performed. Proteins were stained with Coomassie brilliant blue and gels were scanned using a densitometer. We detected spectrin deficiency in 7.4% of cases (2/27), ankyrin deficiency in 29.6% (8/27), combined spectrin and ankyrin deficiency in 3.7% (1/27), band 3 deficiency in 11.1% (3/27) and protein 4.2 deficiency in 14.8% (4/27). Membrane protein deficiencies were not observed in nine cases (33.3%, 9/27). Members of two of seven families tested showed the same protein defects as the proband. Ankyrin deficiency alone and combined with spectrin deficiency accounted for 33.3% of cases (9/27), and they were the most common biochemical defects in Korean HS cases. Protein 4.2 deficiency caused HS more frequently in Koreans than in Caucasians.