Intracerebral inoculation of parkinsonian's cerebrospinal fluid were carried out in 720 mice, under strict observation during 48 weeks. The inoculations led to a mortality rate of 157 mice (21.8%), being 81% (76) in the first, 17% (41) in the second, and 16% (40) after the third one. High mortality rates occurred, most prevalent in the first inoculation and during the first 7 weeks. Dendrite tumefaction and desintegration as well as nerve cell swelling were the ultrastructural changes observed in the brain of mice.