The Wada test or intracarotid amobarbital procedure (IAP) consists of the short inactivation of one brain hemisphere due to the injection of amobarbital or another short-acting anesthetic into the supplying internal carotid artery (ICA). During the subsequent inactivation period, neurological functions such as language and memory can be tested to assess the respective functional reserve capacity of the contralateral hemisphere. Less frequent indications for a Wada test are the assessment of motor function and the identification of secondary bilateral synchrony in EEG. With the advent of high-resolution structural MRI assuring the morphological integrity of the contralateral temporal lobe or hemisphere and functional MRI (fMRI) the number of Wada tests within the presurgical work up of epilepsy patients has decreased. However, it is still method of choice in epilepsy patients with suspected atypical or bilateral language representations according to fMRI, in patients with lesions interfering with the BOLD effect (e.g., cavernomas), and in children or intellectually challenged patients, in which fMRI cannot be used.