A 72-year-old lady presented with recurrent hypoglycaemia and a large pelvic mass. Hypoglycaemia was accompanied by undetectable serum insulin and c-peptide and high insulin-like growth factor II (IGFII) to IGFI ratio. She had undergone successful resection of a large bladder haemangiopericytoma 7 years earlier. A core biopsy was performed, and histology confirmed the recurrence of the haemangiopericytoma. Local palliative radiotherapy resulted in the reduction of IGFII level and IGFII to IGFI ratio and increased insulin, c-peptide and growth hormone (GH) level with long-term amelioration of hypoglycaemic episodes. Clinically and biochemically, radiotherapy was more effective than GH therapy.