Marr argued that a complete description of any information processing device, including the human brain, necessarily involves three levels of description: the computational level, the algorithmic level, and the implementational level. The goal of this chapter is to illustrate the close, but often unstated, relationship between syntactic theory and brain-based studies of sentence processing (both electrophysiological and neuroimaging). The chapter provides a primer for syntacticians on some of the driving questions underlying brain-based studies of sentence processing, as well as some of the primary results of those investigations. Syntactic theories are primarily concerned with properties of the full syntactic representation of a sentence. When it comes to non-invasively studying brain responses to cognitive stimuli, there really are only two widely available options: electrophysiological responses or hemodynamic responses. The syntactic theory allows syntacticians may be well positioned to become central players in the progress toward a cognitive neuroscience of syntax.