A chimeric non-human animal having an in vivo human hepatocyte population, wherein the effects of non-human animal cells on drug metabolism are suppressed or deleted is provided. A method for producing a chimeric non-human animal that lacks a drug-metabolizing system or has a suppressed drug-metabolizing system and is provided with a drug-metabolizing system driven by human hepatocytes, is provided. The method comprises transplanting human hepatocytes into a non-human animal characterized by (i) being immunodeficient, (ii) having liver damage, and (iii) lacking the functions of an endogenous Cyp3a gene.
