An infant newly diagnosed with propionic acidemic coma was managed successfully with total parenteral nutrition (TPN) and continuous infusion of insulin. The urinary excretion of 3-hydroxypropionic acid was reduced to 3% of the admission value in 4 days, gradually decreasing to 1.5% in 16 days. The treatment did not prevent a prolonged episode of thrombocytopenia. The infant tolerated TPN well, except for continued hyper-lactic acidemia (2 to 4 times normal). Metabolic acidosis and mild hyperammonemia recurred only when the patient had sepsis secondary to Candida albicans and Staphylococcus aureus infection. ( J Child Neurol 1992;7(Suppl):S88-S91.)