Intracisternal injection of 30 micrograms 6-hydroxydopamine was used to destroy meningeal cells in the newborn hamster. After 20 or 30 days the cerebella of treated animals showed severe morphological alterations including: an absence of distinct folia anterior to the primary fissure; a disruption of lamination in the same region by the displacement of both Purkinje cells and cerebellar interneurons; a reduction in size and frequency of branching of the medullary tree with anomalous anterobasal branches and splaying; reductions in the area of the molecular layer, the total area occupied by granule cells, the length of the pial surface and the length of the Purkinje cell layer of 29, 21, 57 and 27%, respectively; disorganization of the radially organized glial scaffold by outgrowth of Bergmann glial fibers and displacement of their cell bodies, the Golgi epithelial cells, and anomalous orientation, polarity, size and branching frequency of Purkinje cell dendritic trees. These findings support our earlier hypothesis that the initial destruction of meningeal cells destabilizes the cerebellar surface (basal lamina and glia limitans superficialis) and disorganizes the glial scaffold, while the neuronal cerebellar malformations are secondary to this glial defect.