We report an infant with diaper dermatitis and mild respiratory and enteral infections, treated with a homeopathic mercurial medicine: Mercurius 6a (cinnabar dilute 1 x 10(6)), who thereafter became seriously ill with exacerbation and dissemination of the dermatitis as well as irritability and albuminuria. Mercury urine levels were 60 micrograms/L (reference less than 10 micrograms/L). The homeopathic medicine was suspended but symptoms persisted. Therefore the chelating agent D-penicillamine was administered per os (50 mg/kg/day during 10 days). The clinical conditions improved and urinary levels of mercury decreased to normal values. We concluded that homeopathic medicaments should be recognised as potentially harmful substances.