Functional magnetic resonance imaging (fMRI) enhances the understanding of neuroanatomy and functions of the brain and is becoming an accepted brain-mapping tool for clinicians, researchers, and basic scientists alike. A noninvasive procedure with no known risks, fMRI has an ever-growing list of clinical applications, including presurgical mapping of motor, language, and memory functions. fMRI benefits patients and allows neurosurgeons to be aware of, and to navigate, the precise location of patient-specific eloquent cortices and structural anomalies from a tumor. Optimizing preoperative fMRI requires tailoring the fMRI paradigm to the patient's clinical situation and understanding the pitfalls of fMRI interpretation.