Apolipoprotein C-III (apo C-III) is present in the plasma in apo B containing lipoprotein (apo C-III-LpB) and in non apo B containing lipoprotein (apo C-III-Lp non B). Apo C-III inhibits the lipolysis of triglyceride riche particles and the apo B containing lipoprotein binding to the LDL receptor. A clinical study in myocardial infarction survivors (ECTIM study) shows that apo C-III-LpB is a good marker of atherogenesis. Hypolipidemic drugs as fenofibrate and Maxepa decrease the apo C-III-LpB particles. These studies demonstrate that apo C-III presents an important role in apo B containing lipoprotein particles metabolism and atherogenesis. Furthermore apo C-III levels may be reduced by hypolipidemic drugs.