Three patients were treated after they had deliberately ingested domestic agents containing formic acid. The major complications included the local effects on the oropharynx, oesophagus and stomach, metabolic acidosis, derangement of clotting mechanisms with haemorrhage and shock, widespread intravascular haemolysis, disseminated intravascular coagulation and the acute onset of respiratory and renal failure. All 3 patients died between 2 and 14 days after admission. It is the authors' belief that intensive therapy from the outset to include exchange transfusion, infusion of clotting factors, high dose steroids, ventilatory support and peritoneal or haemodialysis with parenteral nutrition may perhaps offer a better chance for survival.