1. Introduction.- 2. General Aspects of Thromboplastin Calibration.- 3. Orthogonal Regression Equation.- 4. The European Community Bureau of Reference Calibration Study.- 5. A Statistician's Independent Evaluation.- 6. Critical Remarks from a Clinician's Point of View.- Discussion.- 7. The Manufacturers' Calibration Study.- 8. INR Ranges and Targets for Oral Anticoagulation to be Effective and Safe.- Discussion.- 9. The British System of Oral Anticoagulant Control and its Relation with the W.H.O. System: Calibration of the Proposed Second W.H.O. International Reference Thromboplastin (BCT/253).- 10. Anomalies of Thromboplastin Nomenclature.- 11. Comparison of a Highly Sensitive Rabbit Brain Thromboplastin, Dade Thromboplastin FS, with a Human Brain Thromboplastin, Manchester Comparative Thromboplastin.- Comment on Dr. Spaethe's contribution.- 12. Proficiency Testing and Standardization of Prothrombin Time - Potential Use of Thromboplastin Calibration in the United States.- 13. The Relationship between the International Normalized Ratio and the Coumarin-Induced Coagulation Defect.- Discussion.- 14. Joint ICTH/ICSH Proposed Policy Statement with Respect to Reporting the Prothrombin Time in Oral Anticoagulant Control.- Discussion.- 15. A Manufacturer's View of Thromboplastin Calibration (I).- 16. A Manufacturer's View of Thromboplastin Calibration (II).