Considering that butyrate-treated malignant cells can recover in a transitory fashion a non-cancerous phenotype, the authors carried out a pharmacokinetics study of butyric acid injected as sodium or arginine salts for possible antitumor therapies. In the case of 1-14C-labelled butyrate, the appearance of radioactivity in the blood of injected mice is rapid and some of it is maintained for relatively long periods in different organs, mainly the liver. However, no precision can be given about the structure of radioactive compounds in blood and tissues. Using gas-liquid chromatography, the authors studied the metabolism of butyrate in both animals and man. In mice and rabbits, the half-life is less than 5 min. In man, the butyric acid elimination curve can be divided into two parts corresponding to two half-lives: for the first (0.5 min), the slope suggests an accelerated excretion, while for the following (13.7 min), a slow plateau is observed. The rapid elimination of butyrate is a limiting factor for practical applications. However, the lack of toxicity supports its use in human therapy.