Tyrosinemia, also referred to in the literature as tyrosinosis or tyrosyluria, is a disease characterized by elevated levels of sermn tyrosine and by the presence of excess tyrosine, para-hydroxyphenylpyruvic acid (pHPPA), and other phenols in the urine. Among the disorders of amino acid metabolism, tyrosinemia has been studied more than others because of interest in the genetic defects of aromatic amino acid metabolism, e.g. alkaptonuria, albinism, and phenylketonuria. Attempts to simulate these disorders in animals have led to the development of experimental models for the study of tyrosinemia.