Ethylene glycol poisoning is treated mainly by alcohol dehydrogenase inhibition therapy and hemodialysis. Early recognition and initiation of treatment is important because toxic metabolites increase over time by hepatic metabolism; however, there is no confirmative diagnostic tool in our clinical setting. Therefore, diagnosis is dependent on history, high anion gap acidosis, high osmolal gap, etc.. Diagnosis and treatment are delayed in cases where history taking is not possible, such as a mental changed patient. Authors report on two cases of ethylene glycol poisoning by contrasting clinical outcomes, demonstrating the importance of early diagnosis and treatment for achievement of a good outcome.