SUMMARYA 28 year old man presented with partial hypopituitarism and signs of a pituitary tumour. A chromophobe adenoma was partially removed by right frontal craniotomy. Seven years later complete hypopituitarism and hyperprolactinaemia were documented, at which time there was no evidence of tumour recurrence on CT scan. The patient was treated with bromocriptine but the pituitary tumour redeveloped a year later. Nine years after the original operation the first metastasis was demonstrated together with very high prolactin levels. The intracranial metastasis, and the pituitary tumour were removed at a second craniotomy following which the prolactin concentration fell. Further metastases developed subsequently and the patient died 12 years after the initial diagnosis. At autopsy multiple metastases were found in the brain, tumour cells were present in the subarachnoid space and in cerebral veins. The pituitary tumour and secondaries were shown by immunocytochemistry to contain prolactin but not ACTH or growth hormone. This appears to be the third well documented case of a metastasizing, prolactin secreting pituitary tumour.