A 28-year-old woman with inoperable gastric carcinoma was given continuous infusion of 5-fluorouracil (5-FU) and low-dose cisplatin (CDDP) for 4 weeks while receiving intravenous hyperalimentation (IVH). Eleven days after her last treatment, she developed acute diplopia, deafness and gait ataxia, followed by severe confusion. She became markedly acidotic and hypotensive with a systolic blood pressure of 60 mmHg, necessitating intubation, dopamine treatment and hemodialysis for 7 h. She was also given thiamine. Thereafter, her blood pressure stabilized, the acidosis improved, and her deafness, diplopia, and confusion were resolved. This case suggests that FP (5-FU/CDDP) therapy toxicity, manifested as acute metabolic acidosis and Wernicke's encephalopathy, may be associated with IVH and thiamine deficiency.