OBJECTIVES AND METHODS: Methylarginines like asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are formed by post-translation methylation of arginine residues in proteins. ADMA inhibits nitric-oxide synthase and predicts clinical outcomes in various diseases including end stage renal disease (ESRD). SDMA competes with l-arginine for cell entry and is associated with organ failure in patients with severe illness. We investigated the inter-relationships between methylargines, l-arginine and other risk factors and tested the prediction power of methylargines for mortality in a prospective cohort study including 288 ESRD patients. RESULTS: ADMA and SDMA exceeded the upper limit of the corresponding normal range in almost all cases (98% and 100%, respectively) and were inter-related (r=0.30, P