The sensorimotor flow of information can be divided in three steps: perception, processing and reaction. Environmental impulses are conducted through receptors to the central nervous system (CNS). The impulses arriving in the somatosensory cortex are processed through complex interactions between sensory and motor areas. The motor action in response to the environmental changes is transferred from the motor cortex via the pyramidal tract, spinal tracts and motor neurons to the respective muscles. With functional magnetic resonance imaging (fMRI) it is possible to assess somatosensory and motor activation in the different cortical areas involved. Clinically, this information is used to assess the local relationship between brain tumors and functionally important areas. This is important to ensure an optimal individual therapeutic approach with the aim of an as radical as possible tumor resection with preservation of the motor and somatosensory functions. Furthermore, fMRI enables the evaluation of pathological changes of cerebral activation. This review describes the functional somatosensory and motor systems and gives an insight into the potential of fMRI.