The Wada test assesses language dominance and independent hemispheric memory support for patients who are candidates for neurological surgery. The procedure involves the injection of an anesthetic agent into the internal carotid artery to induce temporary anesthesia of one cerebral hemisphere and observing the behavioral response. It predicts the likelihood of language and/or memory complications after surgery. Amobarbital has been the drug of choice. Its recent unavailability has led to the use of other medications, including propofol, etomidate, and methohexital. By injecting drugs into the distal carotid branches, super-selective Wada can localize neurological functions. Functional MRI and other procedures are challenging the Wada test’s eminence. However, the Wada test is still the “gold standard” in many medical centers. This chapter reviews these issues in detail.