Acute intoxication with inorganic fluoride disrupts numerous physiological systems. As a potent acid it acts corrosively on the skin and mucous membranes, producing severe burns. As the most electronegative element it tightly binds many cations essential to homeostasis, producing, for example, profound hypocalcaemia and resultant inhibition of normal blood coagulation. As a metabolic poison it stimulates some enzymes, such as adenylate cyclase, and severely inhibits others, such as Na(+)-K(+)-ATPase and the enzymes of carbohydrate metabolism. Death can result from these processes and also from a delayed, explosive hyperkalaemia. Therapy of acute poisoning is aimed first, at preventing the absorption of fluoride by incorporating it into insoluble fluoride compounds; secondly, at enhancing fluoride tolerance by maintaining normal blood pH and electrolytes, and aggressive general support of the toxic patient; and thirdly, at manipulating renal excretion or removing fluoride with dialysis and haemoperfusion. If the poisoned patient can be supported for 24 hours, the prognosis improves markedly, although delayed toxicity can occur.