Magnetic resonance imaging (MRI) has become an established and invaluable tool in the diagnosis of numerous diseases through its ability to show pathologic contrast in images of soft tissue. More recently, MRI has found application in the study of organ function, principally in the brain and heart. This article deals with MRI imaging of brain function and describes some of the techniques that allow physiological parameters such as cerebral blood volume, cerebral blood oxygenation, and cerebral perfusion to be determined. Additionally, some of the potentially confounding influences in these experiments are discussed.