Deep brain stimulation (DBS) is widely used as a safe and effective medical treatment for certain neurological disorders. It continues to evolve with improving techniques in functional neurosurgery and biomedical device engineering. This paper provides an overview of the enabling science and technology that have allowed DBS to successfully treat certain neurological disorders. It also points toward some of the engineering advances that will enable DBS to yield a more predictable outcome for current indications and to be systematically developed as a treatment for new indications.