The components of centrifugal fractionation of liver homogenates from normal and starved rats were examined for cholesterol synthesis and inhibition thereof. Normal liver particulate matter fractions obtained between 700 to 9000 × g and 9000 to 140,000 × g were active with respect to cholesterol synthesis in the presence of clear supernate obtained by centrifugation at 140,000 × g. The particles alone did not synthesize cholesterol. Particles from liver homogenate of starved rats, recombined with clear supernate from starved rats, lacked synthetic activity but clear supernate from liver homogenate of starved rats showed some activity in the presence of normal particles. Degradation of cholesterol occurred with liver particles (700–9000 × g) from both normal and starved rats: the latter preparation also inhibited cholesterol synthesis. Preliminary incubation of clear supernate from normal rats with particles from starved rats, followed by recentrifugation at 140,000 × g, produced a supernate with synthetic activity equal to that obtained with untreated supernate. Preliminary incubation with normal particles gave a supernate with less synthetic activity. This indicated another difference between particulate matter from normal and starved rats.