||Tyrosine (Tyr) is one of the four standard amino acids containing an aromatic group as a side chain. Its hydrophobicity is one of the main characteristics of this uncharged polar amino acid. In addition to being an essential amino acid Tyr is important in number of biological processes such as the synthesis of neurotransmitters, thyroid hormones, melanine, fumarate and acetoacetate. The pathology of abnormal concentrations of Tyr is well known in diseases including phenylketonuria, hypothyroidism, tyrosinemia, albinism, and alkaptonuria. Tyrosine Assay kit is a simple, yet sensitive assay that is able to detect normal and abnormal concentrations of Tyr in biological fluids. The assay is based on the enzymatic oxidation of Tyr producing a stable signal (OD 492 nm), which is directly proportional to the amount of Tyr. Sample preparation is minimal and does not require strenuous or complicated procedures. The assay can detect as low as 50 μM of Tyr in a variety of biological samples.