We report the enhanced expression of early forms of microtubule-associated proteins (MAPs) in cortical dysplasia in surgical resections from 17 children with intractable epilepsy. Large neurons, which represent one of the characteristic cellular features of cortical dysplasia, showed strong immunoreactivity for MAP1B, as well as the low-molecular-weight isoform of MAP2 (MAP2c). Insitu hybridization with MAP1B antisense riboprobe showed markedly increased hybridization signal intensities in the large neurons, whereas neurons in the normal-appearing cortex and most of the normal-sized neurons in the dysplastic cortex had faint signals. Because MAP2c and MAP1B are early forms of MAPs, which are abundantly expressed in the developing brain and down-regulated in the adult, and are thought to be involved in neuronal outgrowth and plasticity, our results suggest that the structural remodeling of neuronal processes is activated in cortical dysplasia.