The sections in this article are: 1 Anatomy of the Hemoglobin Molecule 2 Molecular Basis for Cooperative Oxygen Binding 3 Allosteric Modification of Oxygen Binding 3.1 Protons 3.1.1 Binding Sites for Bohr Protons 3.2 Organic Phosphates 3.2.1 Metabolic Regulation of 2,3-Diphosphoglycerate in Mammalian Red Blood Cells 3.2.2 Binding of Organic Phosphate to Hemoglobin 3.2.3 Physiological Importance of Organic Phosphates 3.2.4 Interactions Between Organic Phosphates and Chloride 3.2.5 Influence of Organic Phosphates on the Bohr Effect 3.2.6 Regulation of Red Blood Cell PH Through Hemoglobin and Organic Phosphates 3.3 Interaction Between Hemoglobin and Carbon Dioxide 3.3.1 Influence of Carbon Dioxide Binding on Hemoglobin Function 4 Oxygen-Hemoglobin Equilibrium Curve 4.1 General Aspects 4.2 Methodological Aspects 4.2.1 Preparation of Hemoglobin Solutions for Measurements of Oxygen-Hemoglobin Equilibrium Curves 4.2.2 Preparation of Samples for Whole-Blood Measurements 4.2.3 Techniques for Measurement of the Oxygenhemoglobin Equilibrium Curve 5 Oxygen Transport of Hemoglobin During Development 5.1 Embryonic Period 5.2 Fetal Period 5.2.1 Physiological Significance of High Oxygen Affinity of Fetal Blood 5.3 Postnatal Period 6 Effects of Hypoxic Hypoxia 6.1 Animals Residing at High Altitude 6.2 Natives at High Altitude 6.3 Sojourners at High Altitude 7 Kinetics of Oxygen Binding and Dissociation 7.1 Combination and Dissociation Velocity of the First and Last Oxygen-Binding Step 7.2 Overall Rates of Oxygen Association and Dissociation in Hemoglobin Solutions 7.3 Comparison of Oxygen Combination and Dissociation Velocity in Hemoglobin Solutions and Red Blood Cells 8 Pathological Hemoglobins 8.1 Hemoglobins With Altered Oxygen Affinity