Nine original articles dealing with the neurosurgical management of mass lesions of the brain stem and published in the nineties have been reviewed. The manage ment of these lesions remains controversial and the papers reviewed reflect the different attitudes that prevail. They suggest, however, that the experience gained in this field will allow more optimal management of this difficult lesion in the future. Optimal management of patients with brain stem mass lesions certainly requires high-quality neuroimaging, especially MRI. The type of lesions found in the pediatric population are different than in adults, and their management should also be different. Indeed, in children, the MRI characteristics of brain stem lesions, when coupled with the clinical history, match well with the pathological diagnosis and outcome in most cases. Therefore, many authors consider that pathological sampling is not required to initiate further treatment in children. This attitude is, however, controversial and not shared by all neurosurgeons and neuropediatricians. In adults, some authors advocate aggressive surgery, attempting the removal of focal intrinsic tumors using well-defined surgical approaches. Except in non-glial tumors, such as cavernomas and hemangioblastomas, the morbidity remains high and it is difficult to assess the risk versus benefit ratio in term of survival and quality of life. Thus, the direct surgical us approach should be limited to those cases with a clear exophytic tumor that will allow surgical removal with minimal morbidity. In the other cases, stereotactic biopsy represents a valuable alternative and will provide an accurate diagnosis, allowing each patient to be managed with the optimal specific therapy.