The cerebellar granule cell layer and partly the Bergmann glial scaffold arise from a secondary subpial proliferative zone, the external granular layer. Their development can be disrupted by selective destruction of meningeal cells. In order to clarify the mechanisms of meningeal control of cortical development, we have investigated the development of early postnatal rat cerebellar slice explants in different coculture set-ups with meningeal cells and other fibroblasts. Fibroblasts of various sources (1) stimulate migration of undifferentiated neurons from the explants by a diffusible factor and (2) trigger the development of a radial phenotype in glial cells by contact-mediated mechanisms involving basal lamina constituents. These data provide further evidence for the involvement of mesenchymal-epithelial interactions in the development of the cerebellar cortex.