We have used a monoclonal antibody (Jones mAb) to study the expression of gangliosides associated to neuronal migration in the hippocampus of normal and chronic adult epileptic rats. As in other brain regions, the pattern of expression of this ganglioside in the developing rat hippocampus correlates with the migration of cells and processes. In the adult animal, the ganglioside is not expressed, although neuronal migration and process outgrowth have been described in the dentate gyrus of adult animals. Similar negative results were found in adult animals with pilocarpine induced epilepsy in which abnormal neuronal migration has also been suggested and synaptic reorganization of the dentate mossy fibers has been demonstrated. The current results do not help to explain the molecular basis over which epilepsy, in both human and animal models, leads to mossy fiber sprouting and granule cell dispersion.