A case of unilateral cerebellar hypoplasia is presented. This was an incidental finding in a patient with no evidence of neuromuscular or metabolic disease and no past history of trauma, anoxia, or perinatal difficulties. Computed tomographic scans showed posterior fossa asymmetry with underlying unilateral cerebellar hemisphere hypoplasia. In addition, there was overlying skull table thickening and excess petrous pneumatization on the affected side.