The current chapter considers neuronal circuits in the human brain that represent a neuroanatomical basis for the processing of syntactic complexities. We will present data from event-related brain potential studies and from functional and structural brain imaging studies to elucidate the brain’s underpinnings for syntactic processing. The data shall indicate that the processing of syntactic dependencies is subserved by two distinct networks of brain areas, one involving the deep frontal operculum and the anterior part of the superior temporal gyrus (STG), holding responsible for the processing of local dependencies, the other involving Broca’s area and the posterior part of the STG, holding responsible for the processing of hierarchical dependencies. Structural brain data are referred that identify two separate neural fiber pathways for these two networks. These findings are supported by ontogenetic and phylogenetic comparison. The data suggest functional and structural separation for the processing of different levels of syntactic complexity.