In 23 patients with arteriosclerotic cardiovascular disease ranging from 45 to 62 years given sodium dextrothyroxine, serum cholesterol levels were reduced to normal in 11 patients. During the 5 month observation period, mean cholesterol values declined from an initial 284 mg% to 188 mg%. Side effects[long dash]heartburn and nervousness[long dash]were observed in only 2 patients. These subjective symptoms were transitory and did not necessitate discontinuance of the drug. The dextrorotary isomer of thyroxine is an effective cholesteropenic agent with insignificant side effects.