In this article, I review various causes of exogenous myoglobinuria(MU) and its pathogenesis in 26 consecutive patients admitted to emergency room, Asan Medical Center and determine whether there is a relationship between concentration of urine myoglobin(Mb) and acute renal failure(ARF) as a complication of MU. Serum and urine Mb were measured by RIA using myoglobin kit (Daiichi, Inc., Tokyo, Japan). The most common disorder of MU was septic shock with hypotension, followed by crush syndrome, major arterial occlusion by thormbosis, alcohol intoxication with status epilepticus, intoxication of unidentified snake venom and drug ingestion. On the basis of this limited amount of data, there is a significant association between high concentration in urine Mb(> 300 ng/ml) and ARF(Fisher's exact test, p< 0.005). To minimize the chances of development of ARF, routine urine Mb levels should be checked on patients at risk, especially septic shock with hypotension.