The cholesterol storage disease (CSD) BALB/c mouse represents a model of the Niemann-Pick type C (NPC) disease. It is characterized by the accumulation of unesterified cholesterol within various tissues, resulting in fatal neurological lesions. Transplantation of 6x10(6) fetal liver cells from normal allogeneic CBA mice into lethally irradiated CSD mice led to reconstitution of the recipient mice with donor cells. As a result of this stable chimerism, deposition of lipids in tissues was decreased, neuropathy was prevented, and survival was significantly prolonged (over 190 days on average in transplanted mice versus 70 days in untreated mice). Foamy cells containing unesterified cholesterol, observed by filipin staining, were numerous in most tissues from untreated CSD mice; they were significantly fewer in CSD mice treated with fetal liver transplantation at the age of 36-45 days.