Abstract: The invention is directed to a hairless, immunodeficient mouse that is homozygous recessive for a hairless (Hrhr) allele and both B-cell deficient and T-cell deficient. The B-cell and T-cell deficiency is attributed to a homozygous recessive scid allele (Prkdcscid), a homozygous recessive beige allele (Lystbg), or a mutated Rag allele. These mice offer an advantage over nude mouse models used in cancer research because they can be maintained as homozygous breeding pairs and they have greater immune deficits, which permit better growth of xenogenic tumor lines, and rapid assessment of cutaneous and subcutaneous tumors and tissue grafts.