Hydrofluoric acid readily penetrates the skin and mucous membranes, causing deep tissue layer destruction. Dermal exposure can produce hypocalcaemia, hypomagnesaemia, hyperkalaemia, cardiac dysrhythmias and death. We report the case of a 52-year-old man who presented hypocalcaemia and hypomagnesaemia due to occupational dermal contact with hydrofluoric acid. Hypocalcaemia and hypomagnesaemia were corrected by i.v. administration of calcium gluconate and magnesium sulphate.