The great technological improvement in the neurosurgical tools and in the neuroradiological imaging has brought about the diffusion of the stereotactic techniques. They are crucial for the diagnosis and treatment of intracranial expanding lesions of small dimensions or located in sites inaccessible to conventional techniques. The Authors describe the most common systems and methodologies for the stereotactic biopsy. They stress the importance of performing serial explorations which can provide evidence of the heterogeneity of the neoplastic lesion and of the infiltration of the brain adjacent to the tumor.