An 8 year old prepubertal boy presented with raised intracranial pressure, left proptosis and was noted to have galactorrhoea. Cranial computerized tomography revealed a large pituitary tumour infiltrating the cavernous sinus and left orbit. The serum prolactin was 180,600 mU/l (normal value less than 360 mU/l). Prolactinomas are rare in children and galactorrhoea has not previously been reported in a prepubertal child. The management of massive prolactinomas is difficult, but the child presented has made an impressive response to a combination of treatment with surgery, dopamine agonist therapy and radiotherapy.