l-Arginine is considered as a non-essential amino acid for most adult mammalian species, but it is classified as essential for birds, fish, possibly reptiles and also for strict carnivores. The product subject of this assessment is l-arginine produced by fermentation with a genetically modified strain of Corynebacterium glutamicum (KCCM 80099). It is intended to be used in feed and water for drinking for all animal species and categories. The following conclusions refer to the additive ‘L-arginine produced by Corynebacterium glutamicum KCCM 80099’. Neither the genetically modified production strain nor its recombinant DNA were detected in the final product. The additive does not give rise to safety concerns with regard to the genetic modification of the production strain. The use of the additive is safe for target species when supplemented to diets in appropriate amounts, for the consumer and for the environment. The additive is not hazardous by inhalation, is not a skin sensitiser, but is corrosive to skin and eyes. The additive is an effective source of arginine for all species. For the supplemental l-arginine to be as efficacious in ruminants as in non-ruminant species, it requires protection against microbial degradation in the rumen.