This book offers a description of current and recently developed laboratory assays in the field of haemostasis and thrombosis. It is the result of a unique cooperation between experts from more than 60 institutes in 12 European countries, brought together by the ECA T (European Concerted Action on Thrombosis and Disabilities) under the auspices of the Commission of the European Communities in Brussels, Belgium. The ECAT, which was initiated in 1981, designed and performed three prospective clinical studies to establish haemostatic factors as risk indicators of thrombosis. Included were patients with angina pectoris at risk from myocardial infarction, patients undergoing angioplasty at risk from re-stenosis, and patients receiving hip replacement at risk from deep venous thrombosis. Assay procedures were chosen, training courses for technicians held, and essential reagents were supplied from a central source. A quality control assessment scheme served to compare assay results both within and between laboratories. In the angina pectoris study, centres determined most of the assays locally; in the other two studies assays were performed centrally. The need for further quality assessment in Europe Dr J. F. Davidson in Glasgow, led to a separate activity coordinated by including coagulation inhibitors and plasminogen as risk factors for familial venous thrombosis. The Editors hope the ECA T Assay Procedures book will contribute to further harmonization ofhaemostasis assays, and ultimately to their standardization.