The six fractions of cells that differ in the content and ratio of different isoforms of hemoglobin can be isolated using fractional centrifugation of peripheral blood erythrocytes in intact rats. The distribution of hemoglobin in red blood cells is characterized by the fact that if six protein isoforms are determined in whole blood, then only two in the cells of each individual fraction. Red blood cells with isoforms of lower molecular weight contain a lower percentage of hemoglobins with acid-and alkali-resistant properties.