Characterization of the hemoglobins of winter-hibernating, winter-active and summer-active Arctic ground squirrels (Citellus undulatus) by citrate agar electrophoresis and isoelectric focusing (IEF), pH 5.5-8.5, showed no differences in hemoglobin electrophoretic patterns. Previous studies showing alterations in hemoglobins were most likely the result of artifacts due to the use of whole blood. The Arctic ground squirrel's hemoglobin amino terminal sequence was determined for each activity state and was identical in all cases.