Two inbred rabbit strains, JWY-NIBS and NWY-NIBS, were established by full-sib mating in the Nippon Institute for Biological Science, Laboratory Animal Research Station. The origin, breeding history, and biological characteristics of the two inbred strains are as follows. 1. JWY-NIBS: Origin: Japanese white rabbits which had been originally kept at a farm near mount Takao, then transferred to another farm in Fuchu and maintained as a closed colony for a long time. Date of the first full-sib mating: April, 1964. Date of the 20th full-sib mating: June, 1981. Age of maturity: 7-month-old in females, 7.5-month-old in males. Body weight at maturity: 2.8-3.0 kg in females, 2.8-2.9 kg in males. Marker genes: Hemopexin; HxS. Esterase; Est-1s. alpha-Protein; F type. 2. NWY-NIBS: Origin: A strain III of New zealand white rabbits imported from the Jakson Laboratory in USA. Date of the first full-sib mating: November, 1967. Date of the 20th full-sib mating: July, 1982. Age of maturity: 7.5-month-old in females, 8-month-old in males. Body weight at maturity: 2.8-3.0 kg in females, 2.9-3.1 kg in males. Marker genes: Hemopexin; HxF. Esterase; Est-1S. Est-2f. alpha-Protein; S type.