A man with a prolactin secreting pituitary carcinoma was treated by surgery and radiotherapy. Persistent hyperprolactinaemia partially responded to oral bromocriptine for four years. Serum prolactin then rose considerably with rapid, invasive tumour recurrence. Cytotoxic chemotherapy halted tumour progression for twelve months before fatal spread throughout the brain. Failure to normalise serum prolactin with bromocriptine may precede an aggressive course in patients with prolactinoma.