Content: Introduction Phenomenon of Red Blood Cell Aggregation Definitions Historical Aspects Recent History and Future Directions Literature Cited Determinants of Red Blood Cell Aggregation Factors Affecting Red Blood Cell Aggregation Macromolecules as Determinants of Red Blood Cell Aggregation Cellular Factors Determining the Extent of Red Blood Cell Aggregation Literature Cited Mechanism of Red Blood Cell Aggregation Current Models of RBC Aggregation The Depletion Theory for Red Blood Cell Aggregation Evidence Supporting Depletion Hypothesis Concluding Remarks Literature Cited Measurement of Red Blood Cell Aggregation Methods for Quantification of Red Blood Cell Aggregation Sample Preparation for Red Blood Cell Aggregation Measurement Assessment of Red Blood Cell Aggregability Interpretation of the Results Literature Cited Effect of Red Blood Cell Aggregation on In Vitro Blood Rheology Initial Considerations Viscometric Systems Potential Artifacts Affecting Blood Viscometry Rheological Behavior of Blood Literature Cited Effect of Red Blood Cell Aggregation on Tube Flow Historical Perspectives Tube Flow Fahraeus Effect Fahraeus-Lindqvist Effect Effect of Red Blood Cell Aggregation on Tube Flow Conclusion Literature Cited In Vivo Hemodynamics and Red Blood Cell Aggregation Basic Approach to In Vivo Blood Flow In Vivo versus In Vitro Blood Viscosity Experimental Studies Investigating In Vivo Effects of Red Blood Cell Aggregation Hemodynamic Mechanisms Influenced by Red Blood Cell Aggregation Red Blood Cell Aggregation: Good or Bad for Tissue Perfusion? Literature Cited Alterations in Red Blood Cell Aggregation ''Normal'' Ranges of Red Blood Cell Aggregation Alterations of Red Blood Cell Aggregation with Extreme Conditions Alterations of Red Blood Cell Aggregation in Pathophysiological Processes Therapeutic Approach to Red Blood Cell Aggregation Literature Cited Comparative Aspects of Red Blood Cell Aggregation Aggregation Is a Characteristic of Mammalian Red Blood Cells Red Blood Cell Aggregation Characteristics in Various Mammalian Species Correlations with Red Blood Cell Properties Correlation with Other Properties of Species Conclusion Literature Cited Index