We describe an 18-year-old man with acute renal failure due to inadvertent ingestion of antifreeze that contained ethylene glycol (EG). A relatively small amount of EG was ingested, but nausea and vomiting were observed soon after ingestion. During admission to a local hospital, consciousness became impaired and generalized convulsion was noted. He was transferred to our hospital because of rapid deterioration of renal function. Emergency hemodialysis was begun. The patient underwent one treatment session of hemodialysis each day, for a total of 8 hemodialytic sessions before his renal function recovered. Examination of the renal biopsy specimen revealed degeneration of the renal tubular epithelium and presence of intratubular calcium oxalate crystals. The clinical features of the patient were mild except for acute renal failure. These findings suggest that even a small amount of EG will have toxic effects on the kidney.