The diagnosis and management of diffuse brain stem gliomas (DBSGs) remain a challenging problem for the neurosurgeon and neuro-oncologist. Opposing views on the necessity for biopsy have emerged over the last decade. Open biopsy, with its prohibitive morbidity and mortality, has been replaced by stereotactically guided biopsy, with markedly reduced risk. This has been paralleled by improvements in imaging techniques and diagnostic accuracy, which has created reluctance to endorse diagnostic biopsies coupled with the potential of nonrepresentative samples from a heterogeneous tumour mass. For typical DBSGs biopsy is now accepted as unnecessary. We performed a retrospective analysis of radiologically and histologically proven DBSGs in 18 children to assess both morbidity and reliability of our stereotactically guided biopsy procedure.