Novel cholesterol synthesis inhibitors FR171456 and FR173945 were isolated from the culture broth of Sporormiella minima No. 15604. FR171456 strongly inhibited the cholesterol synthesis and up-regulated the LDL-receptor expression in human hepatoma cell line Hep G2. Single oral administration of FR171456 inhibited in vivo hepatic sterol synthesis in rats. And FR171456 shows a significant serum cholesterol-lowering effect in a cholesterol fed rabbit model.