A case of 47-year-old woman with a local relapse of medulloblastoma 23 years after initial presentation is reported. At the age of 24, the patient underwent resection of medulloblastoma of the right cerebellar lobe, followed by the craniospinal orthovoltage irradiation (3600 R to the brain, and 3000 R to the spinal cord). At the 21st year of follow-up, a second cancer originating in the thyroid gland was diagnosed. Thyroidectomy followed by 131-iodotherapy for the papillary cancer was performed. Two years later she was operated for the recurrence of medulloblastoma at the former site. The patient was unfit for chemotherapy due to poor bone marrow reserve following the previous treatment. The reirradiation of the posterior cranial fossa was performed postoperatively. The patient was given 45 Gy in 25 fractions to the recurred tumour volume with 2 cm margin within 41 days. The treatment was performed by 6 MV photons with conformal technique and noncoplanar beams arrangement. The patient is disease free 15 months after relapse of medulloblastoma. The following problems are discussed: late relapse of medulloblastoma, secondary cancers after craniospinal irradiation, and retreatment of CNS tumours.