Dichloroacetate is known to reduce plasma cholesterol and triglyceride in patients with Fredrickson Types IIb or IV hyperlipoproteinemia. We now report the effects of chronic, oral dichloroacetate administration (as the sodium salt) in two patients with severe homozygous familial hypercholesterolemia. Dichloroacetate markedly reduced serum total and low density lipoprotein cholesterol levels and lowered the low density lipoprotein to high density lipoprotein cholesterol ratio. One patient developed a polyneuropathy while receiving dichloroacetate which resolved following discontinuation of the drug. Because of its apparent toxicity, dichloroacetate cannot be recommended for chronic oral use. Investigation of the mechanism of its lipid-lowering effect, however, may provide insight into the pathogenesis and treatment of hypercholesterolemic disorders.