Unlike inorganic arsenic, inorganic trivalent antimony (Sb) is not methylated in vivo. It is excreted in the bile after conjugation with glutathione and also in urine. A significant proportion of that excreted in bile undergoes an enterohepatic circulation. In workers exposed to pentavalent Sb, the urinary Sb excretion is related to the intensity ofexposure. It has been estimated that after eight hours exposure to 500 ug SbIm', the increase of urinary Sb concentration at the end of the shift amounts on average to 35 pg/g creatinine. Antimony (Sb) and its compounds are mainly used for the production of alloys, flame retardants, and in the glass industry. Some derivatives are also used in the treatment of tropical diseases. Antimony resembles arsenic in its chemical properties; both belong to the same group (Va) of the periodic table. Knowledge of the metabolism of inorganic Sb in mammals, however, is more limited than that of arsenic.'2 Studies in animals have suggested that trivalent Sb is excreted mainly in the faeces and to a lesser extent in urine whereas the reverse holds true for pentavalent Sb. Increased urinary excretion of Sb has been found in workers exposed to Sb,03 in a glass producing factory.3This paper summarises the results of experimental studies designed to assess the handling of inorganic trivalent Sb in vivo, in particular to determine