Acetarsone is a pentavalent arsenical compound with antiprotozoal and antihelmintic properties. It was first discovered in 1921 at Pasteur Institute by Ernest Fourneau, and sold under the brand name Stovarsol (fourneau is the French word for stove). Before stovarsol was used in the treatment of congenital syphilis, it had already been used in other diseases : amoebiasis, acquired syphilis, yaws, trypanosomiasis and malaria, and a formidable list of toxic manifestations can be compiled from the literature. Bender (I927) recorded six cases of poisoning with malaise, fever, cedema, jaundice, diarrhoea, albuminuria, bronchitis, coryza and skin troubles, such as diffuse erythema, dryness and pruritus. Of 232 cases of amoebiasis treated by Brown (I935) without a death, thirteen (5.6%) had toxic erythemata, some of them so severe as to amount to exfoliative dermatitis. Although its mechanism of action is not fully known, acetarsone may bind to protein-containing sulfhydryl groups located in the parasite, thereby forming lethal As-S bonds. This may prevent their functioning and eventually kill the parasite.