Neuroimaging techniques that rely on detecting alterations in blood flow may be used to map the cortical localization of cognitive function during task performance. O-15 water positron emission tomography studies have mapped neural networks that subserve language function. These techniques have been adapted to lateralize and localize language function in patients with intractable epilepsy prior to epilepsy surgery. Functional magnetic resonance (fMR) imaging, relying upon fast MR imaging techniques performed during cognitive tasks, allows localization of language areas in individual adults and children and, because there is no radiation exposure, allows for additional or repeat studies in patients. These noninvasive means of language localization may supplant the invasive means of language lateralization (intracarotid amytal procedure) and localization (corticography), and will allow for the continued study of language organization in health and disease.