Reelin is a glycoprotein that acts as a stop signal for neuronal migration during brain ontogenesis. It plays an important role in the remodeling of the hippocampal formation and in stabilizing cortical architecture. We studied immunohistochemically 30 cases of focal cortical dysplasia (FCD) type IIIa to verify whether Reelin could represent the pathogenetic link between HS and cortical dyslamination in the setting of FCD type IIIa. Our results suggest that a subset of FCD type IIIa (namely abnormal cortical layering associated with MTS and GCD type 2) exists in which loss of Reelin appears to be the common pathogenetic basis. On the contrary in the other cases the presence of a common pathogenetic link remains to be demonstrated.