We attempted the breeding experiment in order to establish an inbred strain of disease model animal derived from a spontaneously hyperlipidemic rabbit (HLR). The clinical, pathological features and breeding results of HLR strain were as follows; 1) A prominent clinical feature of this strain was conspicuous elevation of serous lipid ingredients including cholesterol (S-ch), beta-lipoprotein (beta-LP). The S-ch level was 400 +/- 70 mg/dl, the beta-LP level 9.1 +/- 1.5 unit and the total lipid 1146 +/- 270 mg/dl in the HLR strain. These values were approximately 9, 10 and 4 times higher than those of normal rabbits respectively. 2) After sacrifice, aterosclerotic lesions were evident extensively in the aorta and renal arteries. Nodular of plane xanthomas were conspicuous over the articuli digitorum of manus and pedis. 3) HLR strain indicated a striking resemblance of the condition to type III hyperlipidemia in the Frederickson's classification of hyperlipidemia in man. 4) Inbreeding was carried out in two lines, viz. sister-brother mating, parent-offspring mating and back crossing. As the result, the second filial generation showed an incidence of HLR of 15.0%, the third generation 50.0%, and the fourth generation 56.1% respectively. In the fourth generation, the coefficients of inbreeding and relationship were 50% and 72.3% respectively.