THE antilipaemic effect of nicotinic acid is well known1 and the clinical value of this compound as an agent for lowering the content of cholesterol has been demonstrated2,3. Although many explanations have been offered, the mechanism by which nicotinic acid exerts its antilipaemic effect is not known. It is generally agreed, however, that the effect of decreasing cholesterol is unrelated to this compound's known vitamin role as a precursor of pyridine nucleotides, because nicotinamide, which is more readily incorporated into pyridine nucleotides, has little effect on serum cholesterol concentrations in man2,3.