The mammalian cerebellum is subdivided into an elaborate, reproducible array of parasagittal stripes and transverse zones. Stripes and zones are most clearly revealed by the patterns of expression of numerous genes and by the consequences of several naturally-occurring mutations. Because the stripe and zone boundaries are orthogonal, they subdivide the cerebellum into a patchwork grid. How is this elaborate topography created during cerebellar development? This article reviews the evidence for cerebellar regionalization and considers various mechanisms by which it might arise during embryogenesis.