At the Neurosurgical department in Hradec Králové in the course of 50 years (1948–1997) 458 children under 17 years were operated on for various processes in the posterior cranial fossa. The majority, 406 cases, were formed by tumours represented by cerebellar astrocytomas 152 (37.4 %), medulloblastomas 140 (34.5%), gliomas of the brain stem 46 (11.3 %), ependymomas 28 (6.9 %) and other tumours 40 (9.9 %). The postoperative mortality (within one month) was before the introduction of computed tomography (1948–1977), as compared with the era of computed tomography (1978–1997) in cerebellar astrocytomas 8.6% : 4.4 %, in medulloblastomas 14.9% : 2.9 %, in gliomas of the brain stem 21.7% : 23.8%, in ependymomas 18.2% : 6.3 % and in other tumours 40.0 % : 11.5 %. The high initial mortality rate was due to insufficient intracranial decompression, cerebral oedema and impaired circulation of cerebrospinal fluid. Obstruc- tive hydrocephalus in 53 tumours and 25 stenoses of the aqueduct called for Torkildsen’s drainage in 5.4% and catheterization of the aqueduct in 12.2 % of the patients. The most frequent complications in

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