The technique of fiber tracking based on diffusion tensor imaging offers the unique possibility of localizing the white matter pathways of the brain in vivo. In patients with cerebral tumors or space-occupying lesions of the brain, these pathways are often damaged or significantly displaced. Knowledge of the exact location of the lesion with respect to clinically eloquent white matter pathways is of great value to the neurosurgeon in planning the appropriate surgical strategy. We present here preliminary findings using the fiber tracking technique in four patients with space-occupying lesions and discuss the potential and limitations of the technique for lesion localization and neurosurgical planning.