Functional MRI (magnetic resonance imaging) allows one to noninvasively identify various eloquent cortices in the brain. The integration of cortical activation information into radiosurgical treatment planning may provide an alternative to prevent or minimize radiation damage to eloquent cortex. A novel approach of directly integrating the fMRI (functional magnetic resonance imaging) brain map into treatment planning is proposed. Three brain tumor patients have been studied using this method with motor and/or visual paradigms. Brain activation was demonstrated in eloquent cortex at the precentral gyrus (motor area) and medial occipital lobe (visual area). The activation maps were transferred to a treatment planning workstation, (XKnife), and 3D (three-dimensional) activation maps were generated and co-registered to a 3D CT (computed tomography) anatomical data set, which provided the calibration localizer, for treatment planning. Radiosurgery was designed based on both functional and structural information by the medical team consisting of a radiation oncologist, a neurosurgeon and a physicist. The average maximum dose for the tumor was 2113 cGy. The average maximum dose for tissue surrounding the tumor was 1600 cGy. The average dose with fMRI information to the eloquent cortex was 163.4 cGy over three patients, while without fMRI information it was 240.5 cGy. The average percentage dose reduction over three patients is 32%. The results suggest that using this method can reduce the dose to the eloquent cortex. This approach provides the physician with additional information for treatment planning and may spare the patient unnecessary radiation exposure to adjacent eloquent cortices.