In 1992, asymmetrical dimethylarginine (ADMA) was first described as an endogenous inhibitor of the arginine-nitric oxide (NO) pathway. From then, its role in regulating NO production has attracted increasing attention. Nowadays, ADMA is regarded as a novel cardiovascular risk factor. The role of the kidney and the liver in the metabolism of ADMA has been extensively studied and both organs have proven to play a key role in the elimination of ADMA. Although the liver removes ADMA exclusively via degradation by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), the kidney uses both metabolic degradation via DDAH and urinary excretion to eliminate ADMA. Modulating activity and/or expression of DDAH is still under research and may be a potential therapeutic approach to influence ADMA plasma levels. Interestingly, next to its association with cardiovascular disease, ADMA also seems to play a role in other clinical conditions, such as critical illness, hepatic failure, and preeclampsia. To elucidate the clinical significance of ADMA in these conditions, the field of research must be enlarged.