Acute renal failure means that the word does not contain a mild kidney injury. In addition, the criteria for acute renal failure per researcher are different, and it is difficult in interpreting the results of research on acute renal failure. Therefore, rather than acute renal failure, a new term "acute kidney injury" meaning to include all the levels of injury is introduced. In 2002, to diagnose by means of serum creatinine, glomerular filtration rate and urine output, a detailed classification of acute kidney injury, the RIFLE criteria has been proposed. In 2007, the RIFLE criteria by transforming, AKIN criteria has been proposed. The pediatric RIFLE criteria for children has also been proposed. The author reviews here these criteria by comparing them.