Arteriosclerosis and cholesterol cholelithiasis are characterized by abnormal regulation of cholesterol trafficking and solubilization, and subsequent development of the arteriosclerotic plaque in the artery walls and gallstone formation in the gallbladder, respectively. Cholesterol metabolism is controlled by many complex polygenetic - environmental interactions that contribute to the regulation of serum lipoprotein cholesterol levels and biliary cholesterol and bile acids secretion, which constitute the only pathway for sterol elimination from the organism. Much of our understanding of cholesterol metabolism has arisen from studies of the pathways controlling cholesterol synthesis and the uptake and degradation of LDL and HDL lipoproteins. Recently, two new members of the ABC transporter family (ABCG5 and ABCG8 heterodimers) have been discovered in the apical pole of the enterocyte and in the canalicular membrane of hepatocytes. Experiments in genetically engineered mice have demonstrated that ABCG5/G8 represent the physiological canalicular transporter of biliary cholesterol and the intestinal secretory mechanism of absorbed dietary plant sterols. Interestingly, mutation of ABCG5 and or ABCG8 genes in man causes sitosterolemia, a rare genetic disease characterized by massive absorption of plant sterols and premature arteriosclerosis. The potential pharmacological manipulation of biliary cholesterol secretion represents another important therapeutic target to treat hypercholesterolemia, if this manipulation is simultaneously accompanied by measures aimed to avoid gallbladder cholesterol crystallization. The best theoretical drug should decrease serum lipoprotein cholesterol levels, increase biliary cholesterol secretion and fecal elimination and favoring at the same time gallbladder emptying to prevent gallstone formation.