The clinico-pathological study of a new type of familial parkinsonism with striatal degeneration is reported. The inheritance mode was autosomal recessive, and three out of four offspring of married cousins developed parkinsonism in their early adulthood. Their clinical signs were rigidity, bradykinesia, postural instability and dysarthria. These symptoms were slowly progressive and responsive to levodopa therapy to a variable degree. On cerebral magnetic resonance imaging, T2 and proton density-weighted images showed hyperintensity in the bilateral putamina. The neuropathological study of one case revealed atrophy of the bilateral putamina and caudate nuclei, and a severe neuronal loss and gliosis in the putamina. Patchy mosaicism of normal and degenerated tissue was observed in the putamina. A similar mode of the degeneration was mildly seen in the caudate nuclei. The substantia nigra showed atrophy of the pars reticulata, and mild to moderate neuronal loss of the pars compacta with rostral dominance, but no Lewy bodies were observed. These neuropathological findings differed from those of Parkinson's disease or juvenile parkinsonism, but mimic to those of X-linked dystonia parkinsonism (Lubag). It seems that this familial bilateral striatal degeneration is a new variant of familial parkinsonism.