Epidemiologic studies have shown that CHD (arterial thrombosis) and venous thrombosis were closely associated with dietary saturated fat intake. 2. In vitro and in vivo studies are unanimous in that long chain saturated fatty acids, mostly-stearic acid, are thrombogenic, while linoleic acid has protective effects. 3. Stearic acid appears to modify the fatty acid composition of platelet phospholipids resulting in an increase in the aggregating and clotting capacities of platelets. 4. In coronary patients or in subjects eating saturated fats, similar modifications in platelet behaviour can be observed related to changes in platelet phospholipids. Those results appear to confirm the hypothesis that certain dietary saturated fats, in addition to induce hyperlipemia and atherosclerosis, predispose to thrombosis mostly through blood platelets.