These colloquia were organized to stimulate the experience of scientists working in different fields of lipid metabolism and to update the state of the art of lipid and lipoprotein metabolism. The main lectures and communications cover the lipid and lipoprotein structure, metabolism, epidemiology, laboratoral and clinical diagnosis, physiopathology, nutrition and pharmacology. I hope that these proceedings will form a basis for dissemina- tion of knowledge and will promote more research in these important areas. M. J. Halpern v CONTENTS Metabolic and Clinical Significance of the Lipoprotein Family Concept -. . P. Alaupovic Lipids and Proteins of Lipoproteins in Human Atherosclerosis . -. -. 17 P. Avogaro, G. Bittolo-Bon, G. Cazzolato, F. Belussi, and E. Pontoglio Comparison of the Values of HDL-Cholesterol and of Apoprotein Al and B in the A sessment of Coronary Risk . . 25 M. J. Bugugnani, H. Fouye, R. Haiat, and P. Desoutter Apoprotein S Versus SAA Protein 31 C. L. Malmendier and J. P. Ameryckx Isolation of Two Nonidentical Polypeptides from Apolipoprotein B of Human Plasma 47 S. O. Olofsson, K, Bostrom, O. Wiklund, U. Svanberg, and G. Bondjers A Comparative Study of Lipids and HDL-Cholesterol in Old Joggers and Patients with Coronary Infarction . . . . . -. . . . . . 51 W. Schwartzkopff, K. Peslin, F. Nussel, C. Luley, W. Doehrn, and B. Dransfeld 61 Phospholipids and Platelet Aggregation . . . . . . . . L. Douste-Blazy, G. Mauco, B. Perret, M. Plantavid, F. Laffont, M. F. Simon, and H. Chap 67 An Approach to Antiarteriosclerotic Pharmacology . . . J. Segarra Domenech and S.