1-Methyl-2-pyrrolidinone-15N is labelled 1-Methyl-2-pyrrolidinone (M326120) which is a versatile industrial solvent. NMP is currently approved for use only in veterinary pharmaceuticals. The determination of the disposition and metabolism of NMP in the rat will contribute toward understanding the toxicology of this exogenous chemical which man may likely be exposed to in increasing amounts.