We have developed a unique range of ELISA kits to assess Tryptophan metabolism along the Kynurenine pathway. Highly sensitive, featuring low minimal sample volumes, and easy-to-use, our Kynurenines ELISA kits constitute an alternative to LC/MS for the quantification of L-Tryptophan, L-Kynurenine, Kynurenic acid, and Quinolinic acid in biological fluids: cell culture supernatants, serum, plasma, and urine.